WOODEN FLOORS 1LAYING AND REPAIRING

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Translation: Karsten Lundager,University College Vitus Bering Denmark

WOODEN FLOORS 1

THE WOOD INDUSTRYADVISORY COUNCIL(TRÆBRANCHENSOPLYSNINGSRÅD)

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CONTENTS

Floor types..................................... 4

Flooring materials ........................ 7

Substrates .................................... 11

Fasteners and adhesives............. 17

Wood and moisture ........................ 22

Requirements related to moisture 26

Floor heating .................................. 31

Wet rooms...................................... 36

Acoustics ....................................... 38

Joints ............................................ 40

Laying instructions ......................... 43

Renovation ................................... 70

Damages and repairs ..................... 72

Appendix........................................ 75

Wooden floors and

BR requirements............................. 82

Terminology ................................... 83

Literature ...................................... 85

Subject index ................................. 86

2

PREFACE

This handbook demonstrates thoroughlytested methods for the laying of woodenfloors and describes such technicalconditions which must be fulfilled in orderto construct wooden floors correctly. Thechoice of wooden floors and maintenanceare described in WOOD 47, WoodenFloors 2 .

Both handbooks build on practicalexperience and take into consideration suchconditions that are applicable toconstruction work and to wood as a buildingmaterial.

The exposure to moisture duringconstruction and the inappropriatemoistening of the wooden floor during usemay cause undesired damages because notall materials and not all workmanship arecompatible with wooden materials. Mostbuilding materials expand and contractwhen temperature changes, whereas woodexpands and contracst with changinghumidity.

It is important to take into considerationthe particular relation between wood andhumidity both when laying and whenmaintaining wooden floors. The floors mustbe able to contract and expand independentlyin relation to other building components.Also wooden floor should be laid as late aspossible in the building process in order tosecure that the indoor climate is sufficientlydry. In relation to moisture and exposure tomoisture it is important to treat woodenfloors exactly as one would treat fixedfurniture and other furniture

In spite of different constructionprinciples wooden floors are generallymade of a natural product with thevariations in the material whichcharacterizes wood.

The quality of the wooden floor thereforehighly depends on proper grading of woodand on wood quality as well as thesubsequent workmanship and maintenance.There may be variations in the surfacestructure of the wood, in the colour, in thegrain pattern and in the density.

It is such variations which, within certainlimits, add the life and glow characteristicto natural materials.

As wood adjusts to the variations in airhumidity during the seasons of the yearthere will be natural variations in the widthsof the boards and therefore in the widths ofthe gaps between the boards. Normally, thegaps are closed during the summer and openduring the winter.

This handbook primarily addressesconsultants and craftsmen within thebuilding industry, but has been so plannedthat it may be used by clients, real estateadministrators, and do-it-yourself people andas a lecturing aid in building design.

In order to achieve the widest possibleprofessional approach the handbook hasbeen elaborated in conjunction with floormaterial suppliers and trade associationswho have most willingly contributed withprofessional knowledge and practicalexperience.

Advisory Council for the Wood Industry (Træsbranchens Oplysningsråd)

June 2004Bjarne Lund Johansen

3

FLOOR TYPESWooden floors are floors made of boards,strips, blocks or laminated materials with awooden core. Wooden floors may bedivided into two main groups definedby the construction principle:Suspended floors include: Fl oor s on battens (chocked up) Floors on joists

Non-suspended floor include: Float ing floors Glued floors Nailed floors

Suspended floorsSuspended floors are floors resting upon alinear support of joists or battens. The loadon the floor is transferred through theboards and accepted by the underlayingbattens or joists, see figure 1.

Floors on battensBattens are chocked up on an under- layingstructural floor made of such materials asconcrete, clinker concrete or wood in orderto establish a level surface for the woodenfloor

Floors on joistsStructural joists are the basic part of a woodenjoist system on top of basements, crawlspaces and storey partitions. Suspendedwooden floors may be constructed fromboards or long parquet blocks. The boardsmay be traditional solid floorboards orthey may be laminated parquet floorboardsLong parquet blocks are parquet blockswith a length of more than 700 mm. Floorson joists and battens offer ample opportunitiesfor the placing of sound and heat insulatingmaterials in the cavity under the floor. Thecavity may also be used for the running ofheating and electrical installations.

Figure 1 Suspended floors on battens and onstructural joists

Non-suspended floorsNon-suspended wooden floors aresupported throughout the floor surface by astructural sub floor made of such materialsas concrete or building board.

Floating floorsFloating floors can move freely (in relation tothe sub floor) when the wood expands andcontracts with moisture variations (figure 2).

It is common practice to introduce anadditional layer between the wooden floorand the sub floor in order to secure the freemovement of the floor. This layer may bemade of materials contributing to thermal orsound insulation (cork, foam or the like).

4 FLOOR TYPES

Battens(chocked upwith packingpieces)

Floor on battens

Structural joists

Floor on joists

Figure 2 Non–suspended floors - floating

Floating floors may be laid on top of aload distributing board or directly on topof the intermediate layer.

Figure 3 Non-suspended floors – glued/nailed

Glued and nailed floorsGlued and nailed wooden floors arealways fixed firmly on top of a plane andstable structural floor and supportedthroughout the entire surface, see figure 3.

The structural floor can be made ofconcrete, light weight concrete or awooden based subfloor or even afloating floor - for example made ofglue joined boards. On structural wooden joists it will bepossible to use the sub floor as a workfloor during the construction period.The underlay floor could also be an existingfloor where a renovation is desired layinga new floor on top of the existing.

FLOOR MATERIALS 5

Additional layer Glue

Floor fixed with glueon concrete slabstructural floor

Floating floor - ontop of additionallayer (here cork)

GlueMoisture barrier

Additional layer building board

Floating floor onadditional layermade of wood-based buildingboard

Floor fixed with glueon structural floormade of wood-basedbuilding board

Structural subfloor(building board)

Floating floor onstructural sub floormade of wood-based building board

Additional layer

Structuralsubfloor

Floor construction - terminologyThe uppermost independent layer of thefloor, i.e. the floor covering constitutes thefinished floor surface. The floor covering canbe made of planks, parquet blocks, PVC orlinoleum. Applied finishes such as varnish orother surface treatments are not considered asindependent floor coverings.Structural floors are placed under the floorcover but above the structural joists. Thestructural floor must constitute a continuoussurface making it suitable for example as

work floor and as underlay for a thinfloor cover. The structural floor can bemade of building board (wood-based) laid onpressure resistant insulation, or laid onbattens, structural joists, or on a concretescreed.Notice that thin insulation layers like corkbased cardboard etc. are additional layersand not regarded as structural floors.The function of the structural floorconstruction is primarily to accept andtransfer loads. The structural floorconstruction could be wooden joists,concrete slabs etc. See figure 4

.

Figure 4 Floor construction -terminology

Table 1: An overview of different flooring mater ials and their application in different floorconstructions. The highlighted areas indicate that the product can be used for the said purpose.The text indicates limitations.

Floor types Floor materialsFloor -boards

Parquetblocks

Parquetboards

Mosaicparquet

Woodveneerfloorboards

Laminatefloorboards

Endgrainwoodblocks

SuspendedfloorsFloors onbattens or floorjoists

Minimumthickness 20 mm

Longblocksminimum20 mmthickness

Minimum20 mmthickness

Minimum20 mmthickness

Non-suspendedfloorsFloating floors

Only onfloatingsubfloor

Only clipsystem

Only onfloatingsubfloor

Only onfloatingsubfloor

Nailed floors Minimum12 mmthick –secretnailing

Minimum12 mmthick –secretnailing

Minimum12 mmthick –secretnailing

Minimum12 mmthick –secretnailing

Glued floors Shortblocks

Asksupplier*)

* Only in widths as specified by the supplier.

6 FLOOR TYPES

Floor coverAdditional layer

Structural floor

Structural joists

Structural joists +Structural floor =structural floorconstruction

Floor materials

FloorboardsFloorboards are solid boards primarilyproduced from softwoods such as pine,spruce, douglas or pitch pine. Hardwoods areused to a lesser extend for example oak ormerbau.

Floorboards are planed, tongued andgrooved boards, normally produced inwidths ranging from 75 to 180 mm and inthicknesses from 14 to 30 mm.

It is possible to place special orders forthicknesses up to 40 mm and widths up to450. The length is normally between 1.8and 5.4 m. In case boards are ordered asrandom length it is possible that some

planks may be shorter. In case boards areordered with a fixed length, it is likely thatsome planks (normally 5-10%) will beshorter as the producer needs to economizewhen cutting the tree trunk.

Because floorboards look like planks, theyare sometimes called floor planks althoughthe products do not have sufficient thicknessto merit that term (a planed thickness ofminimum 42 mm).

No standards have been defined for thedimensions and profiles of floorboards. Thatis why floorboards from differentmanufacturers will normally not fit together.

Tongue and groove are often placed nearerthe bottom side of the board in order toprovide the floorboards with the thickestpossible wearing layer. The bottom rebate ismade 0.5 mm deeper than the top rebate inorder to secure a tight fit between theboards, see figure 5.

Floorboards are often supplied with so-called stress grooves at the bottom side inorder to counter the natural (cupping)curving in the boards. Stress grooves areonly considered effective when they have adepth corresponding to two thirds of theinitial thickness of the board, i.e. before

drying and planning. Grooves on the bottomside are not always stress grooves but mayalso be so-called guiding grooves used inconnection with the profiling process.

Boards with a minimum thickness of 20mm may be laid directly on floor battens orjoists as a suspended floor. The distancebetween supports shall be determined inaccordance with thickness and load, seetables 3 and 4. Boards less than 20 mm inthickness require the existence of a sub-floor in order to get sufficient support.

FLOOR MATERIALS 7

-Tongue GrooveStress groove

Bottom rebate Guiding groove

Figure 5 Floorboards

Strip floor / parquet blocksParquet blocks are normally single staves insolid wood. The blocks are rectangularwith tongue and groove (T&G). Howeversolid blocks are also available without T&Gsee figure 6.

Parquet blocks are produced fromtraditional European wood species such asbeech, oak and ash but also such exoticspecies as padouk, merbau, doussie andwenge are used.

Parquet blocks are normally 200-700 mmlong and 50-70 mm wide. Parquet blocksare also produced as so-called long blockswith a length of 700-1200 mm.

Parquet blocks are either glued or nailed.Long blocks with a minimum thickness of20 mm may be laid as a suspended floor.

Parquet boardsParquet boards are made from solid parquetblocks joined together in a prefabricationprocess. It is common practice to join twoor three blocks in parallel, using a specialdovetail joint. The boards are supplied witha T&G along all four sides ad are suppliedin length as normal floorboards see figure 7.

Parquet boards can be laid using the samemethods as those used for ordinaryfloorboards, i.e. as a suspended floor whenthe board thickness is minimum 20 or as anailed floor on level structural floor.

Parquet boards may also be applied asfloating floors joined with purpose madeclips, see page 21.

8 FLOOR MATERIALS

Groove-Tongue

Chamfered edge

Figure 6 Parquet blocks

Dovetail joint- Tongue

Groove Groove for clip

Figure 7 Parquet boards

Parquet tilesParquet tiles are factory joined parquetblocks glued together to constitute largerunits, see figure 8. Parquet tiles are laid as aglued floor.

Mosaic parquetMosaic parquet is made of small parquetblocks joined together in order to formpanels/tiles, see figure 8. The blocks may beglued to an open fabric or mesh or joinedwith steel wire. The fabric or mesh isnormally glued to the back side of the panel,but may also be placed on the front side. Inthe latter case it will be removed when thefloor is finally sanded after laying. Mosaicparquet is laid as a glued floor.

Wood veneer floorboardsWood veneer floorboards are normally madeas a three layer laminate.The bottom layer is made of soft wood withfibres oriented along the board. The core ismade of chipboard, plywood, MDF or crossbonded wooden strips. The topmost layerconsists of minimum 2 mm wood veneer. Inmost cases this layer is 3-4 mm thick. Thewood veneer is separated into stavessimilar in appearance to solid parquetblocks, see figure 9. In this way it ispossible to obtain wood veneer floorboardswith appearance similar to floorboards andparquet blocks. See figure 9.

Wood veneer floorboards are laid asnormal floorboards, i.e. as a suspended floorprovided the thickness is minimum 22 mm.They can also be laid as floating floors or asglued or nailed floors.

Figure 9 Woodveneer floorboards

FLOOR MATERIALS 9

Figure 8 Parquet tiles and mosaic parquet

Wood veneer surface

Bottom layer Core

Laminate floorboardsLaminate floorboards are compositefloorboards with either a chipboard or MDFor HDF core that is bonded to a film ofwood effect veneer (lees than 2 mm thick)and covered with a laminated surface. It isnot to be confused with wood veneerfloorboards. The bottom side is coveredwith a counter veneer made of pvc laminate,paper or the like in order to prevent tensionsand in order to maintain planeness of theboard. See figure 10.

Laminate floorboards are supplied withdifferent surfaces, colours and patternsmost of them imitating wood.

Laminate floorboards with a thin layer ofwood veneer are supplied in a variety ofwood species and with surfaces imitatingboards or parquet patterns. All veneeredboards are supplied pre-varnished.

Laminate floorboards and veneeredlaminate boards can be laid as floating floorsor as glued or nailed floors

End grain wood blocksEnd grain wood blocks are rectangular

wooden blocks made of oak, pine, spruceor larch. The length of the blocks shouldnot exceed 1.5 x the width. The blocks areavailable in thicknesses from 18 to 100mm, see figure 11.

The blocks are laid with fibres in verticalposition. They are glued directly to theunderlay using special glue. The bestsuited underlay is a rigid board material.The blocks may also be glued directly ona dry concrete slab. Blocks with a thicknessexceeding 80 mm may alternatively be laidin sand.

Good quality blocks may be used asfloors in assembly rooms and dwellings. Itdoes, however, require a good finish andsurface treatment.

As the surface on this type of floorconsists of end grain it is very susceptibleto moisture from the air as well as moisturefrom cleaning. It is therefore recommendedto avoid direct exposure to moisture and toconsult the manufacturer concerningmoisture expansion and the possible needfor dilatation joints.

Top layer

Figur 10 Laminatefloorboard veneered

Core

Figure 11 End grain wooden blocks

Bottom layer

10 FLOOR MATERIALS

SUBFLOOR

A prior condition to constructing a goodwooden floor is the establishment of a highquality substrate only using materialswith adequate properties.

Floor battensFloor battens are made of solid wood orthey may be made of laminated wood, seefigure 12. Solid wood floor battens shall befree of wane and should have a width ofminimum 45 mm (planed dimension).Laminated battens (for example Kerto) shallhave a width of minimum 40 mm in order toeliminate the risk of splitting (when nailingor screwing). The battens should always beas long as possible as the best result will beachieved with battens in full room length(no joints). Standard lengths go up to 3.9 mand it may be possible to order battens up to4.8 m.

Battens should be planed on the sidefacing the floorboards. The battens must besufficiently straight to meet the sraightnessrequirements shown elsewhere on this page.After laying the battens the sidewaysdeviation should not exceed 5 mm whencompared to a 2 m straightedge (placed onthe concave side of the batten). Warpingis only allowed to an extent whereby abatten placed loosely on

Figure 12 Floor battens: Sawn battens (1), striplaminated battens (2), plywood principle laminatedbattens, Kerto (3). Reference is made to table 5 onpage 47 for blocking up distances for the differenttypes.

Maximum 1/3Minimum 2/3

Figure 14 Floor battens requirements to knots

the floor and with one end fixed against thefloor is leaving a gap of maximum 2 mmper every 2 m batten length, i.e. a battenwith a length of 3.9 m is accepted to have awarp corresponding to maximum 4 mm gap(at the other end)

SUBFLOOR 11

Straightedge, 2 m

Level deviation accepted value

Max. 5 mmStraightedge, 2 m

ITSideways deviation accepted value

Batten

Max. 2 mm

Figure 13 Accepted tolerances floor battens

Knot groupa+b+c=½ d

d or150 mm

Single knot

The battens must be of a qualitycorresponding to the grading criteria appliedin grading class T1. Consequently, singleknots are only allowed to constitute 1/3 ofthe cross sectional area and groups of knotsonly ¼ of the cross sectional area, seefigure 14.

The best result is achieved when themoisture content corresponds to that ofthe floorboards. This will effectivelyreduce squeaking problems.

The moisture content in the battens mustnever exceed 12 %, i.e. the average ofmoisture testing results should be maximum12 %, and any single testing result must notexceed 14 %, see Appendix: Acceptancecheck.

Packing pieces and cradle systemsMaterials used to chock up battens could be:(see figure 15)

Plywood blocks, minimum 100 cm2,for example 100 x 100 mm or 80 x125 mmChip board blocks, minimum 100cm2, for example 100 x 100 mm or 80x 125 mmHard or soft wood fibre board blocksminimum 100 cm2, for example 100 x100 mm or 80 x 125 mmPlastic wedges or plastic towersPlastic or metal bases including accessoryadjustable sub-system.

When a higher block is required it ispossible to use plastic towers (allows formore deflection), plastic or metal bases or asupport made of fixed masonry or castconcrete blocks (no deflection) on top ofwhich the final packing pieces are placed.

Plastic wedges used as packing piecesshall have a documented approvalconcerning life expectancy and loadcarrying capacity ensuring long termdurability. Exposure to excessive heating,for example from close contact with heatingpipes, may reduce life expectancyconsiderably.

Plastic wedges of unknown origin andquality may decompose over time resultingin the settling of the floor which again mayresult in the need to substitute or relay thefloor.

12 SUBFLOOR

Figure 15 Materials used as packing pieces andcradle systems: Plywood blocks (1), hard fibreboard blocks (2), chipboard blocks (3), soft fibreboard blocks (4), plastic wedges (5), woodenwedges (6), plastic tower cradles (7) and adjustablecradle system with plastic or metal bases (8 and 9).

Soft blocksSoft blocks used in order to reduce theeffect of impact sound shall be made of 12-13 mm thick porous wood fibre boards witha density of 225-300 kg/m3 adhered to apressure equalizing board made of minimum12 mm plywood. The blocks shall have anarea of minimum 100 cm2 for example 100 x100 mm, see figure 16.

The use of soft blocks with a smaller areaor a lower density may result in the settlingof the floor during use.

Bitumen feltBitumen felt is used under blocks in orderto establish a sturdy underlay protecting thedpc (and being diffusion tight at the sametime). It is recommended to use pieces ofapproximately 20 x 20 cm, see figure 16.

Figure 16 Soft blocks made of 12-13 mm porouswood fibre board adhered to minimum 12 mmplywood placed on bitumen felt.

Bituminous felt may be used asdpc under floating or glued floors. Thequality shall be PF 2000 (no sand finish) seefigure 18.

Insulation materialsInsulation materials are used in the floorconstruction in order to improve soundor heat insulation, see figure 17.

In batten or joist constructions it isrecommended to insert 100 mm softmineral wool between battens or joists inorder to absorb sound.

In floating floor constructions thefunction of the insulation is to prevent thetransmission of impact sound from the floorto the structural floor and at the same timeto transfer load. With respect to impactsound it is recommend to use an insulationmaterial with resilient characteristicswhereas considerations to strength andstability requires the use of a rigidinsulation material. The required rigidity ofthe insulation material is determined on thebases of the expected load, the thickness ofthe insulation and type of flooring material.

SUBFLOOR 13

Figure 17 Insulation materialsused for floating floors.

Figure 18 Examples of moisture barriersTop: (1) Combination: Plastic, felt and cardboardMiddle: (2) PVC foil in different thicknesses/qualities.Bottom: (3) Bitumen felt PF 2000, no sand finish.

Moisture barriersPlastic foils used as moisture barriers mustbe at least 0.20 mm PE-foil (Polyethylene)in order to have sufficient strength towithstand strain during the constructionperiod. Only foils with a documenteddiffusion tightness and durability should beused, for example complying with SPSVerksnorm 200/2001 (German standard).

Caution should be taken that the foil isnot perforated by a pointed concretesurface.

Plastic foil is a good sliding layer forfloating floors, particularly so when used intwo layers or combined with flooringcardboard or similar products, see figure 18.

Moisture barriers can also be carried outusing bituminous felt, epoxy or specialglues:

Bitumen felt glued to the subfloor, seepage 21.Cast asphalt with a thickness of 20 mm.Epoxy is applied in thin layers one atthe time.An impartial documentation verifyingthat the product is efficient as a moisturebarrier must be available. Whenapplying, the prescribed thickness shall beobserved as experience shows that themoisture barring ability is beingdrastically reduced when the layerthickness is too small - this may casesubsequent damage to the wooden floor.Special glues - MS-glues are primarilyfunctioning as a barrier retardingmoisture penetration and only to alimited extend as an effective moisturebarrier, see page 20.

14 SUBFLOOR

Flooring cardboardFlooring cardboard is used as underlay forflooring planks, parquet and flooringpanels in order to reduce clatter. Flooringcardboard is a non impregnated cardboardwith a weight of roughly 500 g/m2, seefigure 19.

Foam plastic, cork sheet, or similarFoam plastic, cork sheet or similar productsplaced loosely under wooden floors serveas a pressure equalizer and sliding layer atthe same time. The products also contributeto improving acoustics as they preventclattering between floor and underlay andreduce impact sound. Some products alsofunction as a moisture barrier eliminating theneed for an additional moisture barrier, seefigure 19.

In order to secure that the productspossess relevant characteristics anddurability, only such products recommendedby the floor manufacturer should be used.

Rubber cork/cork rubberSheet rubber cork contributes to thereduction of impact sound and to improvedflexibility in the floor. The effect dependson the thickness and composition of theproduct, see figure 19.

Figure 19 Clatter impact sound reducing materialsfor example flooring cardboard (1), flooring felt (2),foam plastic (3), plastic granulate (4), cork dustsheet (5), cork sheet (6) and rubber cork (7).

SUBFLOOR 15

Structural joistsStructural joists functioning as underlay forsuspended floors shall be aligned forming aplane surface. Alternatively a plane surfaceshall be established by the application of anadditional plank/batten on top of or on theside of the structural joists. Additionalplanks/battens shall have a minimum width of45 mm in order to avoid splitting whennailing/screwing the floor.

Joists should be chosen with considerationto the risk of warping; i.e. with minimumtendency to warping, The need to reestablisha plane surface may be minimized by usinglaminated wooden joists (or HQL).

The best result is achieved when themoisture content in the joists corresponds tothat of the floorboards. In case the moisturecontent in the joists is too high there is a riskof floor settlement due to shrinkage whenthe timber dries. The higher the joist is thebigger is the problem. The moisture contentin the joists must not exceed 13 %, i.e. theaverage of moisture testing results should bemaximum 13 %, and any single testing resultmust not exceed 15 %. See Appendix:Acceptance check.

Concrete slabWhen a concrete slab is used as underlay fornailed or glued wooden floors it is requiredto level the surface using a self levellingcompound, a smoothing compound or ascreed.

When wooden floors are glued to aconcrete slab the surface must be cleaned ofconcrete slur as the slur layer does not havesufficient strength to absorb tension that mayoccur as a consequence of moisturemovements in wooden floors

For further information concerning concreteslabs reference is made to Concrete floorconstructions elaborated by the CementManufacturers (Cementfa-brikkernestekniske Oplysningskontor), 1994concerning workmanship concrete floorsand also GSO Floor Facts (GSOGulvfacta) concerning levelling of floors.

ScreedsScreeds are used for the levelling ofconcrete slabs. Screeds may be based oncement, anhydrite or magnetite. Screeds canalso be made from cast asphalt which at thesame time will function as an effectivemoisture barrier.

Screeds are normally laid in thicknessesof + 15 mm. The properties of the screeddepend on type and composition. In casethe floor is a non-suspended wooden floor itis in most cases necessary to skim thesurface in order to obtain a sufficiently levelsurface.

For further information on screedsreference is made to GSO Floor Facts(GSO gulvfakta).

SandSand used as underlay for floating floorsshall be well graded kiln dried quarts sand.All fractions of the grain curve must berepresented in order to secure sufficientpacking after application and compression.

16 SUBFLOOR

FIXINGS

A variety of fixings such as nails, screws,glue and clips are used when laying woodenfloors.

Nails, screws and staplesPlanks in suspended floors are fixed tobattens or joists using square nails, pinnails, screws, air gun nails or staples.

Wooden floors may be nailed from aboveor using secret (hidden) nailing. When airgun nails are used only secret nailing isrecommended. Nailing from above ensuresa better fixing of individual planks as itallows for dimensional changes across theplank.

On the other hand, secret nailing has theadvantage that planks are pushed together(manual nailing), see figure 20, page 18.

When nailing hardwoods it is required topre-bore before nailing or screwing. Thedrill used for pre-boring must be slightlysmaller in diameter than the nails or screwsused, for example a 3.5 mm drill used for 4.2mm screws.

Table 2 indicates dimensions of nails andscrews to be used for different boardthicknesses. As battens and joists do expandand contract in accordance with humidity, itis not recommended to use fixings longerthan those indicated in the table as doing somay increase the probability of squeaking.

Table 2 Recommended dimensions on nails and screws for floorboards laid on battens or joists. The samescrew dimensions may be used when fixing floorboards to an underlay made of chipboard, boards or the like.Hot dip galvanized nails provide the best grip in wood. Be careful not to use nails or screws longer than thoserecommended as doing so may increase the probability of squeaking when the battens or joists expand andcontract. For direct fixing in concrete it is recommended to use special screws, for example Monta-flex. Whenin doubt, always consult the supplier of nails and screws.

Nails Air gun nails ScrewsPlank thicknessin mm -nails/finishing

nailsStaples T-pin nails Twisted

nailsMonta-flexscrews

Chipboardscrews

12-15 1.8x40 M-32 mm1) l.8x381)

F-14 2.0x382)

F-14 2.0x453)

4.2x45

20-23 Solidpine/spruce

2.8x65 2,5x651) TS 2,3x652) 3)

4030-2½"2)4.2x45 5.0x45

Solidhardwood;

2.8x65 2.5x651)

4030-2½2)4.2x45 5.0x45

Wood veneerfloorboards

2.5x55 N-50 mm 1)

S-16 502)TS 2.3 x 652) 4.2x45 5.0x45

25-26 3.1x80 4.2x45 5.0x5528-30 3.4x90 4.2x55 5.0x7535 3.8x100 4.2x75 5.0x751) Manufacturer:Ottensten

2) Manufacturer:Unimerco

3) For planks with a width between 100 mmand 150 mm

17 FIXINGS

NailsChoice of nail type depends on wood speciesand floor type. As a rule of thumb squarenails are used for manual nailing and twistednails are used for air gun nailing insoftwoods such as pine and spruce. Staplesshould only be used when recommended bythe floor manufacturer.

When fixing hard woods such as oak orbeech, pin nails are used for manual nailingand T-pin nails for air gun fixing, see figures21 and 22.

Nailing should only be carried out usinghot dip galvanized nails as experince showsthat they have the best withdrawalresistance. Also, contrary to bare steel nails,galvanized nails do not cause discolourationwhich reduces such risk in light coloureddelicate planks.

Traditionally wooden floors are handnailed, and this method is still consideredthe safest particularly so when laying solidfloor planks in large dimensions in order tosecure that the planks are pushed properlytogether and are securely fixed tobattens/joists.

Figure 20 Fixing methods using nails or screws

Air gun nailing is used for certainfloorboards but should only be used whenrecommended by the floor manufacturer.When nailing with an air gun it isimportant to press the flooring materialhard agains the underlay in order to secureproper fixing. Pressing with the air gunitself is in most cases insufficient.

Staples T-nails

Figure 21 Nail type for hand nailingTwisted nails

Figure 22 Nail types used for air gun.

18 FIXINGS

Nailed from above Ssecret nailing

Finishingnails(brads)

nails Flooring nails

ScrewsThe choice of screws depends on thescrewing principle adopted (from above orsecret). When screwing from above, ø 5 mmpartially threaded chipboard screws areused. This is a type of screw which has nothread immediately below the head andthus ensuring a better fit of the floor plankagainst the underlay. When applyingsecret screwing, special screws as forexample Monta-flex are used. This screwhas a high withdrawal resistance in wood,wooden boards and in concrete underlay,see figure 23.

When screwing from above it isrecommended to pre-bore a minimum 6 mmdeep hole using a 10 or 15 mm drill in orderto countersink the screws. Subsequently theholes are covered using a wooden plugmade of off cuts using a wood plug cutter,see figure 24. The plugs are glued fixing thegrains in the same direction as the grains inthe flooring planks. When the glue is drythe plugs are cut off flush with the over sideand the planks are sanded.

Wooden underlayPlanks fixed on structural sub floors made ofchipboard, plywood or wooden boards maybe screw- fixed provided the sub floor layson beams or joists. The sub floor must havesufficient thickness to secure satisfactoryadherence.

Figure 24 Secret fixing from above usingchipboard screws covered with a wooden plug.

In sub floors made of chipboard the screwsmust be sufficiently long to penetrate thechipboard. Chipboard screws or specialscrews like for example Plata-flex areused.

The nailing and screwing of floatingfloors should only be carried out whenadvised by the floor manufacturer.

When using secret screwing it is arequirement that the floor planks havethickness of minimum 12 mm. f

Concrete underlaySpecial screws for example Monta-flex, areused when fixing directly on concrete. Pre-boring is required using a drill with adiameter slightly smaller than the screwdiameter, for example a 3.5 mm drill for4.5 mm screws. The screw may be fixeddirectly into the pre-bored hole without theuse of plugs.

Repairing squeaking floorsExisting squeaking floors laying on battensor joists may be nailed from above usingspecial nails such as annular ring nails ortwisted flooring for example 3.5 x 55 mmfor 20-22 flooring planks and 3.5x 65 mmnails for 25-28 mm flooring planks.

Figure 23 Screw types

FIXINGS 19

Wooden plug

Floor

Screw

Batten

Chipboardscrews

Monta-Flex

Plata-Flex

GlueGlues used for the adherence of or gluingtogether of floorboards must chosenconsulting the recommendations issued bythe floor manufacturer in order to ensurethat the glue is compatible with the woodenfloor and the underlay as well as being ableto resist whatever loads may occur. Thesurface to be glued must be clean, dry andauitable for gluing. Manufacturer sinstructions concerning priming,consumption, application etc. must becomplied with in order to secure a goodresult.

Gluing entire faceWhen gluing the entire face of a woodenfloor it is required that the underlay is level,i.e. level deviations maximum ± 2 mmalong a 2 m straightedge and withoutcraters or pointed edges in order to secureproper contact between materials.Levelness of surfaces is described in detailin Appendix: Levelness

The glue to be used is so-called parquetglue, either in the form of water baseddispersion glue or MS glue, i.e. glue basedon Modified Silicone. The latter is moreexpensive but has the advantage that it isfree of water and to a certain extendfunctions as a moisture barrier, see below.The glue must not be too thin.

Wooden floors must not be glued until theresidual moisture content in the underlay issufficiently low, or until an effectivemoisture barrier has been inserted, see moreabout moisture barriers on page 14.

When using dispersion glues the residualmoisture content must not exceed 65%relative humidity, whereas the similar limitfor MS glues is 85% residual moisturecontent (does depend on glue brand),measured at temperatures between 17 and25 °C.

The adherence of wooden floors shall takeplace within a certain period of time, the so-called open time, in order to ensuremaximum bonding. The fixing time isnormally approximately 15 minutes, butdepends on the materials to be glued and onmoisture and temperature conditions in theroom.

The fixing time is short for materials with ahigh absorption rate such as particle boardand certain softwoods whereas materialslike bitumen cardboard and rubber corkallow for a longer fixing time. Whenapplying glue it is advisable to consider theglue s open time in order to ensure that thelaying may be carried out within the limitof the open time.

Floor glue requirementsFrom a wood technical viewpoint the glueshould have the below listed properties:

Low absolute water content in order toavoid deformation of wooden floormaterials as a result of unilateralmoisture exposure on the underside.Ability to fill in such a way that contactcan be established between glue and theflooring material even in unfavourablesituations, for example when there aresmall cavities in the underlay.Rapid fixation, maintaining theblock/plank in a fixed position in gluejointElasticity allowing the glue to absorbwhatever movements there may occur inthe glue jointSufficient strength

When gluing under difficult circumstances,for example on surfaces with littleabsorption or the gluing of floor elements inlarge dimensions (planks) it is advisable touse one or two component glues withoutwater. The use of such glues may, however,cause work environmental problems as thebonding agent in most cases is based onpolyurethane.

Gluing tongue and grooveThe purpose of gluing the tongue andgroove joint in floating floors is primarily toensure that movement is being transferredfrom board to board (by creating a coherentfloor surface). In this way the individualblocks or boards function together, andvertical forces may be accepted withoutunacceptable deflection. Further, the gluedjoint may serve to prevent the penetration ofwater when cleaning the floor.

20 FIXINGS

PVA glue is normally used when gluingtongue and groove joints. In order toensure maximum strength of the joint it isimperative to choose glue that iscompatible with the wood species and alsoto ensure that the glue fills , and is waterresistant, in order to prevent damagescaused by surface treatment and cleaning.The glue type normally used is a so-calledwinter glue (class D3).

Gluing bitumen cardboardWhen bitumen cardboard is used as a

moisture barrier it may be glued to theunderlaying concrete slab using parquet glueor a dispersion glue. When doing so theresidual moisture content in the concretemust not exceed 85% (RH) and capillary riseof ground moisture must not occur.

ClipsSome floorboards may be joined by the useof steel clips. Clips are used for floatingfloors. The clips are slotted into a milledgroove at the backside of the floorboardand connect two neighbouring boards. Indoing so, it is ensured that the boards canmove individually in the horizontaldirection without being pushed apart andthe total movement of the floor is reduced,see figure 25.

Click-jointsSpecially designed for floating floors are anumber of floorboards with a self lockingtongue and groove. When the boards arelaid they are clicked together and requireno further fixing, see figure 25.

Figure 25 As an alternative to gluing tongue andgroove, floating floors may be laid usingmechanical joints in the form of steel clips(2) orclick-joints(1).

FIXINGS 21

WOOD ANDMOISTURE

Wood shrinks and expands in accordancewith air humidity and temperature. In orderto get a good result, it is important toconsider this particular characteristic whendesigning and constructing wooden floors.

Why does wood shrink?The cellular walls in the living tree aresaturated with water, and the cell cavitiesare also filled with water. Wood shrinkswhen the water confined in the cellularwalls dries out. The cellulose in thecellular walls has the property that itabsorbs water from the air and expands

when the air is moist and contracts when theair is dry. Hence, the moisture content anddimension of the wood will always adjust tobe in equilibrium with the relative humidityand temperature of the surrounding air, seefigure 26.

The shrinking and expansion of wood inaccordance with variations in air humidity isthe reason why wooden floors shall be laidkeeping a distance to surrounding buildingcomponents allowing for expansion whenthe wood is exposed to moisture. This alsoimplies the need to lay wooden floors aslate as possible in the building processwaiting for the building to dry out and thusreducing the amount of moisture present.See section The building site andrequirements related to moisture .

Relative air humidity (per cent) Shrinkage (per cent) fromfreshly cut

Figure 26 Graphic illustration of equilibrium moisture content (left) shows the connection between relativeair humidity and moisture content in wood at approximately 20 °C, and the graph to the right showscalculation of shrinkage when changing equilibrium moisture content.

22 WOOD AND MOISTURE

Tem['.

Fyr

] ;are f ir vs.« mpe; egret iKonstructionstra;

Ovm 0rrin; pak 'icvet

Uienllj TS ___o\er-d; ikket

Lejl ghed ;vis (ipvar-"med; run

C'entral-opvamederim

Raiialsvinc Tangenlials

Dry rot danger

Structuraltimber

Temperature approximately 20oC

Kiln dryingrequired Outdoor

coveredconstructions

Occationallyheated rooms

Rooms withcentral heating

Pine

Radialshrinkage

Tangentialshrinkage

How does wood shrink?All fibres in a freshly cut tree are watersaturated. Later, as the wood dries there willbe dimensional changes (shrinkage) more orless corresponding to the reduction of water.Similarly, wood will expand when exposedto moisture. Expansion and contraction arecharacterized by taking place in threedominant directions, see figure 27.

Tangentially along the annular rings(circular in the trunk)Radially- Perpendicular to the annualrings (along pith rays)Axially- Along fibres (longitudinaldirection)

Figure 27 The three dominant directions forshrinkage and expansion of wood

Normally, the tangential shrinkage isapproximately twice as big as the radialshrinkage. The axial shrinkage is onlycorresponding to somewhere between onetenth and one twentieth of the radialshrinkage and for the same reason it maybe disregarded in most cases.

Items with pith are subject to one or moreshrinkage splits extending from surface topith and as a consequence they are not fit tobe used for flooring, see figure 28.

There may be considerable differencesbetween the density of the bottom part andthe top part of a trunk and thereby also bigvariation in shrinkage and moistureconditions.

Shrinkage split

Figure 28 Items with pith are subject toshrinkage splits depending on the position ofthe pith in the board.

How much does wood shrink?It is often necessary to be able to calculateby how much a certain dimension ischanged as a result of varying moisturecontent in the wood (which, as explainedabove, will vary in accordance withvarying air humidity). As a realisticaverage, which may be applied to a numberof commonly used wood species, it may beassumed, that the change of 1 % in woodmoisture content results in a dimensionalshrinkage of approximately 0.15 % (1.5mm/m) radially, and approximately 0.30 %(3.0 mm/m) tangentially. When calculatingexpansion the same values may be applied.

In case the trunk is cut tangentially orradially, see figure 29, it is possible to applythe two mentioned shrinkage percentagesdirectly. In reality planks may often be cutin between the two positions and it istherefore required to apply a mediumshrinkage value of 0.22% (2.2 mm/m)

WOOD AND MOISTURE 23

Shrinkage split

Pith

Pith

Radially

Tangentially

Radial cuts

Figure 29 Shrinkage and expansion of wooddepends on conversion principle applied/annualring position.

Axially

Tangentialconversion

How moisture influences woodenfloorsWhen choosing wooden floor type and alsowhen constructing the floor it is importantto consider the inevitable dimensionalchanges caused by seasonal variations inair humidity, see figure 30.

It is not possible to avoid gaps betweenfloorboards, but it is possible to predict thesize of future gaps simply by choosing theright floor. In this context the term gap isused to describe the space betweenneighbouring boards or blocks in the floor.The size of the gap may be reduced asfollows:

Use narrow boards in stead of wide boardsbecause the size of the gap corresponds toboard width.Choose products with small dimensionalchanges as a consequence of changed airhumidity.Control climate, for example by the use ofair humidifiers in office buildings duringthe winter in order to avoid the drying outof wood.Avoid the use of floor heating systems andradiation heating systems placed in theceiling.

Grams of water per m3 air

Jan. Mar. May Jul. Sep. Nov.Feb. Apr. Jun. Aug. Oct. Dec.

Figure 30 Typical variation in the relative humidity(RH) inside and outside during the year. The relativehumidity is at its maximum inside from August toOctober, and at its lowest from December to March.(SBI direction 178).The RH in office buildings andthe like is often considerably lower that indicated inthe graph.

10-board measurementWhen laying a wooden floor it is importantto ensure that the floor can absorbmovements caused by moisture. This isoften done by use of the so-called 10-boardmeasurement.The10-board measurement is defined as theexpected width of 10 boards when exposedto maximum moisture. This is typically inthe autumn where an average of 13 %moisture content may be expected in thefloorboards. When laying the floor withlower moisture content, for example kilndried to 8 % it must be ensured that a smallgap is established between the boards/blocksfor example by placing thin spacers betweenthe boards. The 10-board measurementshall be controlled at regular intervalsduring the laying of the floor.

Wood veneer floorboards and soft woodfloorboards, for example pine, are normallylaid without observing the 10-boardmeasurement.

The 10-board measurement depends on:Width of boardsMaximum expected air humidity.Wood species (expected change in board

width)Annular ring orientation (radial or

tangential conversion)

The 10-board measurement is mainly usedwhen laying floors type:

Hardwood parquet boards (nailed)Solid parquet blocks with T&G glued tothe sub floor.Parquet blocks (nailed)

SpacersUntil recently it has been common practiceto observe compliance with the 10-boardmeasurement simply by basing the laying onexperience whereby the contractor wouldcheck the prescribed 10-board measurementat regular intervals during laying procedure.

In order to ensure uniform spacing it isrecommended to use so-called spacers, i.e.small pieces of plastic with a thicknesscorresponding exactly to the gap required inorder to comply with the prescribed 10-boardmeasurement. The use of such spacers willmake the constant checking procedureredundant as the spacers will ensurecompliance with the prescribed 10-boardmeasurement.

24 WOOD AND MOISTURE

RH %

RH o ut

RH in

INOUT

Examples

WOOD AND MOISTURE 25

Some examples showing to what degreemoisture influences dimensionalchanges of a wooden floor.

Example 1When a floorboard has been stored forsome time at approximately 20°C andexposed to approximately 78 % RH it willhave a moisture content of approximately16 %. If the RH is changed to 40 % andthe temperature is maintained at 20°C thewood will discharge water to the air andthe moisture content will adjust toapproximately 8 %, see figure 26. Thus,the moisture content will be reduced by8 % which will result in the followingshrinkage:Tangential shrinkage: 0.30 x 8 = 2.4 %Radial shrinkage 0.15x8 = 1.2 %Suppose the board is cut tangentially witha width of 100 mm and 16 % moisturecontent, it will, at 8% moisture contenthave a width of: 100 - (0.3 % x 8 x 100) =97.6 mm.Suppose the board is radially cut, thewidth will be: 100 - (0.15 % x8 x 100) =98.8 mm.Suppose the board is cut somewhere inbetween radially and tangentially thewidth will be: 100 - (0.22 % x8 x 100) =98.2 mm.For wood species (or products) withsmall dimensional changes caused bymoisture variations, the shrinkage maybe reduced by 50 %, whereas theshrinkage in wood species with largerdimensional changes may be increasedby 50 %.

The shrinkage in the longitudinaldirection is normally less then one tenthof width shrinkage.Example 2A traditional wooden floor has 18 boardsper 2 m. The boards are laid withoutspacing. After some month the gapsbetween the boards will vary in size from0 to 5 mm.

The total width of the17 gaps has beenmeasured by the use of feeler gauge andis 48 mm which corresponds to 2.4 %across the 2 m floor.

An average shrinkage of 0.22 % forevery 1 % change in moisture contentwill result in (2.4 %: 0.22 %) = 11 %change in moisture content of the boardsin order to cause a shrinkage of 2.4 %. Asthe actual moisture content is measuredto 7 % it can be concluded that themoisture content was 7 + 11 = 18 %when the boards were laid.

Example 3A floor consists of 100 mm widefloorboards with a moisture content of 8%. The floor is laid in a room with 23 °Cand 40 % RH, which corresponds toequilibrium moisture content of 8% inthe wood. 10 boards will under theseconditions give a width of 1000 mm,provided they are laid without gaps.

It is, however, assumed that the RH inthe room will increase to 65-70 % duringthe summer period corresponding to amoisture content of 13 % in the wood.Exposed to these conditions each boardwill expand by (0.22 % x 5 % x 100 mm)= 1.1 mm (cf. example 1). In order toallow for this expansion it is required tolay the boards with a gaps of 1.1 mmbetween neighbouring boards, i.e. 10boards will require a total width of (1000mm + 10 x 1.1 mm) = 1011 mm, whichin this case will be the 10-boardmeasurement..

During winter, the temperature may be23 °C and the RH 25 % corresponding to adrop in wood moisture content to 6 %.Using summer conditions as starting pointthis means that a board during the driestperiod will shrink approximately (0.22 %x (13 - 6) % x 100) = 1.5 mm. It can thusbe expected that a floor laid under abovementioned assumptions will have 1.5 mmwide gaps between the boards during thedriest period.

Moisture protection -requirements

Design and construction assumptions

Avoiding excessive exposure to moisture orexposure to moisture during a longer periodare preconditions for the use of wood in floorconstructions. Neither must the floor beexposed to excessive drying out. Suchexposures may result in the risk of rot or dryrot when the moisture content exceeds 20 %(weight), and it may also cause undesirabledimensional changes and deformations.

In the subsequent section it will bedemonstrated how to construct woodenfloors avoiding moisture problems. In officebuildings, where the production of moistureis normally at a minimum, there is a risk ofextreme drying out during periods with frost.This may result in shrinkage and as result ofthis in larger gaps in wooden floors,particularly so in floors constituting largeplanes without or with limited possibilitiesfor movement. In some cases it may benecessary to use humidification during thecoldest and driest periods of the year in orderto avoid damages.

In order to ensure correct construction ofwooden floors, particularly with respect tomoisture, it is advisable to follow theguidelines laid down in SBI-Direction 178:Moisture insulation of buildings. See alsoSBI-Directions 184: Heat insulation ofbuildings and 189: Single family houses insulation, moisture protection etc. offeringconcrete examples of constructions meetingcurrent requirements in terms of moistureprotection and heat insulation.

Outside the buildingThe terrain must slope away from the buildingin order to allow for the effective drainingaway of surface water. In flat terrain theslope shall be minimum 1:50. In slopingterrain it is required to level the ground on theside of the building with the highest terrainand it is recommended to establish anintercepting drain at the intersection betweenthe naturally sloping terrain and the adjustedterrain.

Sloping terrain

Figure 31 Adjustment of site profile ensures theleading away of surface water and drainage iscarried out to the extend necessary.

Paved terraces shall be established with aminimum slope of 1:40 in order to preservethe slope also in the event where thepavement settles, see figure 31.

Ground supported floorWhen constructing a ground supported floor,measures must be taken to prevent theabsorption of ground moisture. This may bedone by the insertion of a capillary breakinglayer. Residuous moisture in the concreteslab must be prevented from entering thewooden floor by the insertion of a dpc on topof the slab. s in this dpc must have anoverlap of minimum 200 mm. The jointsshould also be additionally secured by theuse of tape or butyl rubber sealant strip.The dpc is lead close to the wall and anairtight joint is established between the dpcand the dpm in the wall (if any). This alsosecures against the penetration of radon, seefigure 32.

In order to avoid condensation ofmoist air from the room on the top sideof the dpc, it is required to place at least

26 MOISTURE PROTECTION - REQUIREMENTS

Perimeter drain

Flat terrain

Intercepting drain

Figure 32 The placing of dpc and dpm inconstructions with floating floors on groundsupported slab.

Figure 33 The placing of dpc, dpm and insulationin constructions with suspended floors on floorbatten on ground supported slab.

half the insulation under the dpc. Inpractice this is most often done by placinghalf the insulation under the concrete slab,see figure 33.

When carrying out renovation works, it isoften only possible to place insulation ontop of the dpc. In such instances it isrecommended to use maximum 50 mminsulation in order to avoid the risk ofcondensation on the topside. Requiredadditional insulation will, in this case, haveto be carried out as foundation insulation.

Heating pipes under wooden floors mustbe insulated separately and effectively inorder to avoid the drying out of floorboards.Also, measures should be taken to place thepipes on the warm side of the insulation.

When a diffusion tight floor covering (forexample vinyl or linoleum) is used on asuspended floor on floor battens it isrequired to make cut outs in the skirtingboard in order to allow the floorconstruction to adjust to the humidity of theair in the room. In this case a cavity ofminimum 30 mm must be established on topof the insulation material in order to allowthe room air to ventilate the underside of thefloor.

Figure 34 Establishing additional ventilation infloors on floor batten covered with a diffusion tightfloor covering (for example vinyl or linoleum).

MOISTURE PROTECTION - REQUIREMENTS 27

dpmWooden floordpc Insulation

dpm

Wooden floordpcInsulation

Minimum slope

Ventilation

Diffusion tightfloor covering'

Insulation

Minimumslope

Cut outs inskirting board

Ground supported floor in unheatedbuildingsThe temperature in unheated buildings, suchas holiday cottages, will, during winter, behigher in the ground under the building thanit is inside the building. Hence, the moistureflow will, during winter, go from the groundthrough the ground supported floor and intothe house. In such buildings it is importantto establish the moisture barrier (dpc)correctly. No moisture sensitive materialsmust be placed under the dpc and joints inthe dpc as well as joints to other buildingcomponents must be airtight in order toavoid the risk of condensation on theunderside of a diffusion tight layer. This isalso the reason why the use of diffusion tightfloor coverings should be avoided inunheated or occasionally heated buildingswith a ground supported floor. G

Crawl spacesIn crawl space decks consisting of woodenfloors on joists it is particularly important tomaintain the humidity of the air in the crawlspavc at the lowest level possible. It isrecommended to establish a dpc at thebottom of the crawl space in order to preventthe ingress of moisture from the groundbelow. It is also required to establishsufficient ventilation. Figure 35 shows thesize of and the placing of necessaryventilation openings.In order to prevent the ingress of radon it isrecommended to place a dpm under thewooden floor.

BasementsThere is always a risk connected to thelaying of wooden floors in basements. Onething is certain: If the basement is not drythe wooden floor will not last!! If moisture ispresent, the floor will be exposed toexcessive dimensional changes. Beforelaying wooden floors in new buildings allmoisture must be ventilated away until thebasement is sufficiently dry. In unheatedbasements the RH will, especially duringsummer, reach 90 % which is too high forthe use of wooden floors. A modest heatingof the basement may reduce the RH to 75%during summer provided there is nomoisture penetration through leakages in

Figure 35 The placing of dpc, dpm and ventilationopenings in constructions with wooden floors onjoists (crawl space deck).

external walls or capillary rise of groundmoisture.

The external basement wall shall bedrained and the drain must be connected tothe perimeter drain in order to prevent thelocal occurrence of water pressure againstthe external wall. The outer side of thebasement external wall shall have a doublecoating of liquid bitumen applied on top of arendered or rough cast surface or by the useof specially designed PVC drainage sheetingpreventing the penetration of moisture.

With respect to moisture it is advisable tocarry out heat insulation on the outer sideof the wall and on the outer side of possibledrainage sheeting.

Under the basement floor it is required toestablish a capillary breaking layerpreventing the absorption of moisture fromthe ground. The best solution is to place theheat insulation under the concrete slab. Thisinsulation may depending on the choice ofmaterials be carried out as a combinedheat insulating and capillary breaking layer,see figure 36.

Provided the basement construction iscarried out along the above describedrecommendations and, provided it isheated, it is possible to lay a wooden floorfollowing the same guidelines as thoseapplicable to a normal ground supportedfloor. It is required to place a dpm on theconcrete slab before laying the woodenfloor. Joints in the dpm shall overlap byminimum 200 mm and the joint betweendpm and wall shall be airtight.

28 MOISTURE PROTECTION - REQUIREMENTS

DpmWooden floorInsulation

DpcVentilation

Dpc

Slopeminimum1:50

Figure 36 The placing of dpc, dpm and insulationin constructions with a floating wooden floor onstorey partitions and on ground supported floorsin basements.

When renovating old houses it is often awish to establish wooden floors. In suchcases it is required to carry out a moistureinsulation of the constructions. The floorconstruction principles are similar to thoseused in new buildings. In case the roomheight is low, it is possible to use a floatingfloor construction with a moisture andpressure resistant insulation as the loadcarrying underlay. The dpc can be placedbetween insulation and wooden floor orunder the insulation (in case the quality ofthe insulation is inferior to or equals 50 mmmineral wool lambda class 39). For furtherinformation concerning the renovation ofold basements, reference is made to SBI-Direction 178.

Storey partitionsIn order to eliminate the risk of problemsoriginating from construction moisture it isrecommended to place a dpc on top of newconcrete or light weight concrete deckstorey partitions. It is not required to place adpc on top of existing and dry deckconstructions.

Moisture requirements on buildingsite.The dimension of the wood depends on themoisture content which again depends onthe relative humidity (RH) and temperatureof the surroundings. As the relativehumidity changes with the seasons and alsowith the use of the room so will thedimensions of the wood change. It is veryimportant to consider this aspect whendesigning and laying wooden floors.

In order to avoid unnecessary moisteningit is important to lay the floors as late aspossible in the building process. Thebuilding shall be closed, dry and heatedbefore laying the floor. All such works asmay cause the generation of moisture, forexample plastering and basic paint workshall be terminated before the flooring starts.The RH in the building shall be inequilibrium with normal RH for the season,i.e. 35-65 % relative humidity atapproximately 20°C.

When concrete or light weight concreteelements are used it will, in most cases, benecessary to wait for a couple of monthsbefore laying the wooden floor. Ifnecessary, it may be required to usedehumidifiers. Before laying wooden floorson new concrete or light weight concretedecks it is required to measure the moisturecontent in the deck, see Appendix:Measuring moisture content in concrete.

Insulation materials etc. shall be dry. Incase blocking up has been carried out usingconcrete or brickwork such elements mustbe cured and dry.

In case the building has not been properlydried out, the relative humidity will be veryhigh and the wood will expand after thelaying and later, when the wood dries out,the gaps between the boards will be verywide. In case there is too little spacearound the floor the expansion may causethe floor to pop up or in the worst case topush out surrounding walls.

MOISTURE PROTECTION - REQUIREMENTS 29

DpmInsulationWooden floor

- Dpc

Wooden floorDpcInsulation

Drain

Slope,minimum1:50

Insulationand drain

When investigating the moisture conditionsbefore laying wooden floors on concrete it isnot suficient only to measure the relativehumidity of the air but it is also required tomeasure the moisture content in theconcrete. The reason why is that ventilationmay reduce the relative humidity of the airwithout reducing the moisture content in theconcrete.

In case wooden floors are to be used underconditions where it is only required to secureagainst moderate construction moisture fromunderlaying concrete, i.e. a pore moisturecontent of 60-90 % RH, it is possible to avoidmoistening the wood by using a PE-foilminimum 0.20 mm thick. This dpc shall belaid with minimum 200 mm overlap on top ofthe moist concrete before laying the woodenfloor.

Flooring materials - moisturerequirementsFloorboards and parquet blocks arenormally supplied kiln dried and wrapped ina strong PE-foil with a moisture content of 8± 2 %. 2/3 of the lot should have moisturecontent between 7 and 9 %. The moisturecontent in joists, floor batten and blocksshould, as far as possible, correspond to themoisture content in the supplied floor.

At the point of laying the average moisturecontent in floor batten should not exceed 12% and in joists it should not exceed 13 %. Inpractice this means that the average value of12 % (13 %) must be complied with and nosingle values of moisture content in excess of14 % (for battens) and 15 % (for joists) areaccepted see Appendix: Acceptance check.

In cases where it is not possible to get asupply of flooring materials with correctmoisture content, it is imperative to deliverthe flooring materials well in advanceallowing sufficient time for acclimatization,i.e. to attain equilibrium with the temperatureand moisture conditions in the room beforethe actual laying. This process may takeseveral weeks even when the boards arestacked using piling sticks. Laying a woodenfloor with excessive moisture content mayresult in the occurrence of larger gapsbetween the boards when the wood dries out.

30 MOISTURE PROTECTION – REQUIREMENTS

Check list – laying wooden floors The relative humidity in the buildingshall be between 35 and 65 %,(depending on the season) and thetemperature approximately 20°C.The building must be closed and theheating system operational and in use.The moisture content in concrete andlight weight concrete shall be inequilibrium with the relative humidity ofthe air for the season in question, i.e. thepore moisture content shall be 35-65 %relative humidity. In the case of concreteor light weight concrete elements it maytake a couple of months to attainequilibrium. In situ cast concrete mayrequire much more time.Insulation materials etc. shall be dryWhen blocking up is made of masonryor concrete it must be cured and dry.A dpc for example a 0.20 mm PE-foilshall be laid before laying the floor inorder to protect the floor againstconstruction moisture.The wooden floor material shall have amoisture content of 8 ± 2 % of which2/3 of the lot should have a moisturecontent between 7 and 9 %.

When wooden floor materials are kilndried to specifications they should notbe unpacked before the laying.

The moisture content in joists and floorbatten should correspond to themoisture content in the wooden floor.The average moisture content shouldnot exceed 12 % in the case of battensand 13 % in the case of joists and nosingle value must exceed 14 and 15 %respectively.In case the wood is not supplied kilndried, time must be allowed for thewood to obtain equilibrium with themoisture and temperature conditionsexisting in the room.

Wooden materials, glue, caulkingcompounds and similar accessoriesshould be acclimatized for at least 24hours before use. This could be done bystoring such materials inside the roomwhere they will be used.

FLOOR HEATING

Floor heating systems are primarily used inorder to avoid the use of radiators and inorder to achieve a good distribution of heatinside the room. Traditionally, floor heatingsystems have been used in floors withceramic tile covering in bathrooms , butduring recent years an increased used hasbeen observed in all other rooms of thehouse and also in other floor types , forexample in wooden floors.

In new and well insulated houses it is,under normal circumstances, possible toheat a house using a floor heating systemonly. In older houses where the insulationdoes not live up to current requirements it isnormally required to use supplementaryheating sources, for example radiators inorder to meet the heat demand.

It should be noted that wood is a relativelywell-insulating material. As a result woodenfloors, to the touch, feel more comfortable(warmer) than other floor coverings evenwithout floor heating. Thus, from the pointof view of comfort there is no need to usefloor heating in wooden floors in well-insulated houses.

When installing floor heating systemsunder wooden floors the followingconditions shall be observed:

The temperature shall be low in order toavoid the drying out of the wood. Thesuppliers normally require that the surfacetemperature does not exceed 25-27°C.The heat distribution below the floor shallbe even, not only to ensure maximumcomfort, but also to achieve sufficientheat radiation. It is therefore important tolay heating pipes or cables in such a waythat no major variances in temperatureoccur on the surface.

Only such materials and constructionprinciples, including floor heating systems,as recommended by the supplier of thewooden floor should be used. In this contextthe supplier of the floor is required tosupply information concerning the

maximum temperature to which the floormay be exposed and the heating system shallbe constructed in such a way that thistemperature is not exceeded.

In floors where boards or blocks can moveindependently it must be expected at leastduring the heating season that the gapsbetween the boards will be slightly largerthan normal. This is caused by the heatingof the floor which will cause the drying outof the wood and as a consequence largershrinkage across the boards, see examplebelow. Considering this shrinkage it isadvisable to use materials with as littleshrinkage as possible.

One consequence of using floor heating infloors on battens is the heating of thebattens. As a consequence the battens willdry out more than usual. For this reason it isparticularly important that the battens aredry when laying the floor as the extradrying out of the battens will causeadditional shrinkage and thereby increasedrisk of squeaking floors see more aboutthis on page 73. It is therefore required toensure that the battens are dried until theyhave the same moisture content as thefloorboards, i.e. a moisture content of8 ± 2 %. In order to achieve this it is oftenrequired to stack the battens for a period of8-14 days inside the room where they willbe used. Notice that prefabricated battensproduced from kiln dried wood may alsorequire additional drying in case they havebeen stored for a longer period in an

FLOOR HEATING 31

Example:22 x 125 mm pine floorboards are laid on floorbatten. During the year, the moisture contentwill vary between 6 % during winter and 13 %during summer. It is anticipated that the gapsbetween the boards are totally closed duringthe summer. When, in winter, the floor is mostdry there will be a gap of (13-6) x 0.22 % of125 mm = 1.9 mm. In case of floor heating theaverage temperature will increase from 21 to30°C and the moisture content during winterwill drop to approximately 4 %. Thus the gapwill increase to (13 - 4) x 0.22 % of 125 mm =2.5 mm.

unheated warehouse or at the timbermerchants.

Floating floors which are glue-jointed inthe T&G will not have the same problemwith larger gaps between the boards duringthe winter. On the other hand, the gapbetween the surrounding walls and thefloor may be bigger. In case the floor isloaded with heavy furniture along the wallsthere is an increased risk that the floor maysplit, see more about this on page 74.

Whether the floor heating system is water-borne or electric, it is possible to obtain aneven heat distribution under the floor asshown in figures 37-40.

Before laying the wooden floor it isimportant that all such works that maygenerate moisture, for example masonry workor paintwork, are terminated and the floorheating system must have been working for aperiod of at least 14 days. The heating systemis switched off at least 2 days before layingthe floor.

Heating systems used in wooden floorsare purpose made systems, i.e. the systemsare constructed with independent heatingcircuits supplied with an automatic devicecontrolling the floor temperature. Ifpossible, it is recommended to use a presettemperature control device which does notallow for temperatures above the levelrecommended by the floor manufacturer.

Temperature adjustment should take placegradually as sudden temperature changesmay cause splitting of the wood.

In general, it is not recommended to laywooden floors on top of existing floors withold floor heating systems which are notsupplied with automatic control devices fortemperature control.

Floor heating systemsFigures 37-39 show three constructionprinciples using light constructions where it ispossible to control the floor heating with a timeconstant of 1-2 hours, i.e. it is possible to adjustthe room temperature fast, for example whenthe room is subject to insolation (sun throughwindows) or when there is a need to reduce thetemperature during night.

Heating pipes between battens or betweenjoistsWhen heating pipes are placed betweenbattens or joists it is common practice toclip the pipes into so-called heatdistributing panels placed in close contactwith the underside of the floor in order toobtain a good temperature distribution.

The heat distributing panels are producedwith a groove into which the pipe fits, seefigure 37. It is required to use pipes with adiameter corresponding to the size of thegroove in order to ensure good contactbetween pipe and panel. The pipes shouldnot touch the underside of the floor.

It is common practice to use anintermediate layer such as flooringcardboard or felt in order to reduceclattering and squeaking, see figure 37.

Heating pipes on top of battens or joistsWhen the heating pipes are placed on top ofthe joists or battens it is required to place anadditional layer of boards or battensperpendicular to the direction of the joists orbattens. This layer serves as underlay for theheat distributing panels. Otherwise theconstruction is carried out as describedabove, see figure 38.

Boards are used in cases where chipboardis used as a structural floor serving asunderlay for a floating wooden floor. Thedimension of the chipboard is defined inaccordance with the distance between thejoists of floor batten as the additional layerof boards is not considered to be loadcarrying.

Battens/planks are used as underlay forthe heat distributing panels in cases wherethe floorboards are laid parallel to joists orfloor battens. In this case the additionallayer is load carrying and the battens/planksshall be dimensioned in accordance withtable 5, where the blocking up distance willbe equal to the distance between the floorbatten/joists. The blocking up distance mybe reduced by inserting additional floorbatten or joists.

32 FLOOR HEATING

Heating pipes on heat distributingpanels

InsulationJoistsBoards (25x100 mm) onbattens c/c 600 mm

Figure 37 Heating pipes placed on heatdistributing panels which again are placed on topboards placed on structural joists or floor battens.The heating pipes cross the joists in the zone outsidethe end of the joist in order not to weaken the joistby cutting into it. Floorboards are screwed or nailed.

Figure 38 Heating pipes on heating distributingpanels placed on structural joists. Here shown withchipboard as structural floor and floating woodenfloor. May also be carried out with structuralbattens (replacing additional boards) andfloorboards.

Heating pipes in floor heating slabs.Floor heating slabs consist of one layer ofinsulation material (usually polystyrene)and heat distributing metal sheets. The floorheating slabs are supplied with ready madegrooves fitting the heating pipes. The slabsare placed on top of a structural underlay andthe pipes are placed in the gooves. Anintermediate layer (flooring cardboard or felt)is placed between the slabs and a pressuredistributing subfloor made of chipboard ontop of which a floating floor may be laid, seefigure 39.

Wooden floor possibly on top ofpressure distributing sub floor

Figure 39 Heating pipes in »Floor heating slab«,i.e. insulating slabs made of polystyrene suppliedwith heat distributing metal panels. An intermediatelayer of flooring cardboard or felt is placed betweenthe heating slab and the floor above in order toreduce impact sound. The floor is laid as a floatingfloor.

FLOOR HEATING 33

Chipboard as structural floor

Intermediate layer

Heating pipes on heatdistributing panels

Floating wooden floor

Intermediate layer

Damp proof courseThe purpose of placing a dpc in wooden floorswith floor heating is to secure the wood againstundesired moistening. The placing depends onthe construction in question and also depends onwhere in the building the floor is placed. It isrecommended to consult with SBI-Direction 178or to ask advice from the floor supplier.

Insulation

Intermediate layer

dpc

Concrete slab

Intermediate layer

Floor boards orparquet boards

Addtional boards carrying heatingpipes

Heating pipes on floor heatingslab

Maximum effect for floor heatingsystems: The effect should neverexceed 100 W/m2

Embedded heating pipes and cablesWhen embedding heating pipes or cables inconcrete there should be a cover layer ofminimum 30-70 mm on top of the pipes orthe cables in order to achieve an even heatdistribution and the wooden floor should beplaced as close as possible to the underlay,see figure 40. An efficient dpc, for examplebitumen felt, should be placed between theconcrete and the wooden floor in order toprevent the transportation of moisture(released from the concrete by the heating)from concrete to wood.

It is difficult to adjust the heat radiationrapidly because of the heat accumulatingcapacity of the concrete which causes thetime constant for this type of floor to be ashigh as 12 hours.Heavy constructions used to be considered anadvantage as they were able to accumulateenergy during periods with sun and releasethe energy again during the night With the thickness of insulation appliedtoday this capacity is no longer interesting. .

Figure 40 The embedding of heating pipes inconcrete gives an even heat distribution. Theplacing of dpc and insulation depends on theconstruction in question consult experts in thefield.

Figure 41 Electric cables in levelling compoundshould be so placed that they are covered withminimum 10 mm levelling compound to ensureeven heat distribution.

Electric heating mats/electric cables placedin levelling compound.Electric-based heating systems may also befitted using levelling compounds. The totalheight of this construction is very low. Thecables may be placed directly on top of aninorganic underlay or placed on a woodenbased underlay with minimum 5 mmlevelling compound between the cable andunderlay. In order to ensure an even heatdistribution the thickness of the levellingcompound on top of the cables should be atleast 10 mm, see figure 41. It isrecommended to use a fibre reinforcedlevelling compound which is capable ofresisting foreseen temperatures.

One significant difference between electricsystems and water borne systems is the factthat the electric system gives a fixed effectand as a result high temperatures may occurunder thick carpets, furniture etc. In order toavoid excessive heating it is recommendedonly to use such cables and mats which arecapable of supplying the heating requiredwith the lowest effect possible and neverexceeding 100W/m2. A low effect providesthe same comfort as a high effect, but will ofcourse result in a slower regulation of thetemperature. In practice, this is not a problemas the temperature is normally set to a certainsurface or room temperature once and for all.

34 FLOOR HEATING

Wooden floor

GlueLevelling compound, minimum 10 mm

Levelling compound.Electric-cables

Wooden floor

Intermediate layerPossibly dpc

Concrete slab with 30-70 mm cover layer

Reinforcement meshPossibly insulation

Concrete slab

Aspects related to energyIt is imperative to follow carefully theinstructions issued by the floor manufacturerwhen laying and using wooden floors withfloor heating including recommendationsconcerning the types of floor heating andconstructions which may be used, and whattemperatures the floor may be exposed to.

Under furniture and floor coverings, forexample under book cases and carpets with agood heat insulating capacity the floortemperature may be higher than thetemperature in other parts of the floor. Thismay cause extra large gaps between thefloorboards during winter.

The limited surface temperatureobtainable also determines the effect whichmay be released by a floor heating system.As a guideline it may be reckoned that afloor heating system may release an effect asexpressed in the following formula:

Released effect = 10 x (tf - tr) W/m2,where tf is the surface temperature of thefloor and tr is the room temperature.When calculating with this formula usingthe most commonly occurring surfacetemperatures we get the results shown intable 3.

Table 3 Released effect in wooden floors withcommonly occurring surface temperatures and witha room temperature of 21°C.In comparison the energy need for new single familyhouses insulated in accordance with BR-S 98:45 W/m2

Maximum surface temperatureThe surface temperature in the woodenfloor must not exceed 25-27°C.Depending on thickness this correspondsto the following temperatures on theunderside of the wooden floor:

22 mm thickness: 33-34°C14 mm thickness: 30-32°C10 mm thickness: 28-30°C

The temperature difference betweenupper- and underside depends on floorthickness, wood specie and materialcomposition (solid/laminated).

Surface temperature °C Effect W/m2

25 °C 4026°C 5027°C 60

Best in well insulated housesThe heating with floor heating is onlysufficient in new and well insulated houses.When remodelling houses it is recommendedto use supplementary heat supply in additionto floor heating, for example in the form of

FLOOR HEATING 35

When placing floor heatingunder wooden floors –remember:

Floor heating may only be usedtogether with such products suitable forthe purpose and approved by thesupplier.The floor heating system shall ensure aneven heat distribution on the floorsurface. The floor heating system shall besupplied with a preset temperaturecontrol device which does not allow fortemperatures above the levelrecommended by the floor manufacturer.Only such floor heating systems asrecommended by the floormanufacturer may be used.The need for supplementary heating fromradiators is likely in older houses.Floor batten/joists shal be dry in order toavoid squeaking.Avoid the laying of wooden floors ontop of old floors with floor heatingwithout automatic temperature control.Laths placed as underlay for heatdistributing panels are countersunkbetween joists or floor battenIn electric-based flooring systems theeffect must not exceed 100 W/m2.In water-borne heating systems the pipesmust not touch the floorboards.

radiators. This is due to the fact that theinsulation in older houses is normallyinferior to present requirements and as aconsequence the effect needed is higher.

Larger energy consumptionIn general larger energy consumption maybe expected when using floor heatingcompared to the use of radiators. This is thereason why the building regulations BRS 98require additional insulation in groundsupported floors and in storey partitionsfacing the outside or facing ventilated crawlspaces when such floors are supplied withfloor heating. In these constructions themaximum U-values are: s

In multi-storeybuildings:0.12 in stead of 0.15In single family housesand the like.:0,.12 in stead of 0.15

Also floors above heated rooms should besupplied with insulation under floor heatingsystems in order to prevent the undesiredheating of the room below and in order tosave energy.

WET ROOMS

Because of its beautiful texture it hasbecome very tempting to use wood asflooring material in wet rooms. However, itis against regulations to substitutetraditional ceramic tiles or PVC floors withwooden floors, cf. B&B-Direction 200Wet rooms . The reasons are several:Generally speaking, wood is not suited to

withstand constant exposure to water orexcessive humidity as such exposure maycause the growth of fungi and worst casescenario rot or dry rot. The combinationof elevated humidity and high temperature common to bathrooms is very productiveto the growth of dry rot.

Wooden floorboards are narrow and as aconsequence there are many joints. Add tothis that most floors are laid as so-calledships plank with caulked joints (elastic

caulking compound).As a rule of thumb, the water tightness in

wet rooms must not be based on the use ofelastic joints because such joints are not longterm watertight.

Even in cases where a watertightmembrane has been used there is a risk thatwater may penetrate the joints which maycause the growth of fungi and or bad odour.Seen in this light, wooden floors in wetrooms are only accepted in the followingcases:

When fixed on top of a finished, approvedand consequently watertight floor, i.e.inclusive floor covering of ceramic tilesor PVC.In areas of the room not frequentlyexposed to water.On the condition that the wooden floormay be removed again without damagingwet room constructions.

In general it is not recommended to usewooden floors in wet rooms because of theincreased risk of obnoxious smells, growthof fungi and possibly rot or dry rot in caseof excessive humidity.

36 WET ROOMS

Under all circumstances it must beconsidered that wooden floors will have ashorter lifetime compared to other surfacesused in a bathroom and as a result they mustbe substituted more frequently.

It is an obligation to inform the client, thatthe risks of inconveniences related to the useof wooden floors as supplementary floorcovering, is entirely his own responsibility.Should the client still want to use woodenfloors, such floors must only be laid in lessexposed areas of the wet room, and, in orderto minimize the risk of inconveniences,observing the guidelines indicated in thesummary on page 38, figure 42.

The wooden covering shall be kept wellaway from areas particularly exposed tomoisture, for example shower stalls, bathtubs and floor drains, se figure 41. No pipepenetrations are accepted in the wooden floorand it is not accepted to establish a floordrain, see figure 43 and the guidelines onpage 38.

The wooden floor must be treated andmaintained in accordance withmanufacturer s instructions. As the use ofwooden floors in wet rooms increase therisk of bad odours, fungi attack etc., it isrecommended:

To immediately remove free water fromthe floor surfaceTo pay special attention to any signs of orsymptoms, which may indicate waterpenetration, moisture or the presence offungi?

Figure 43 It is not accepted to construct woodenfloors in wet rooms with floor drains or pipepenetrations.

Figure 42 Wooden floors are onlyaccepted in wet rooms provided they layon top of an approved watertight wet roomfloor and observing a distance requirementof minimum 500 mm away from showerstalls, bath tub and floor drain.

WET ROOMS 37

Wooden floors in wet roomsAre beautiful- but only serve as decorationCannot substitute ceramic tiles or PVC

flooring as watertight underlay.May cause risk of fungi attack etc.See guidelines for the use of wooden floorsin wet rooms on page 38.

ASPECTS RELATEDTO SOUND

Floors on battensIn case there is a demand to the reduction ofimpact sound on wooden floors it isrequired to place a piece of soft material, forexample a porous wooden fibre with athickness of maximum 13 mm and glued toa pressure distributing piece of plywoodsee page 12. The thickness of the softmaterial shall be equal in all blocks used forblocking up.

The packing pieces shall be fixed to thebattens using toe-nailing, i.e. a nail enteringthe batten on the side and continuing at anangle into the block or wedge, see figure 58.The nail must not enter the soft material.

An alternative packing method to woodenblocks (combined with soft blocks) is the useof plastic wedges. When using wedges madeof hard type plastic, the impact sound levelmay be increased by 0-4 dB. Always contactthe wedge manufacturer for furtherinformation concerning impact soundreduction.

Battens and floorboards shall be kept at adistance of minimum 10 mm away fromsurrounding walls and pipes penetrating thefloor.

When electric cables and heating pipesrun under the floor it is required to keep adistance of 10 mm between cable / pipe andbatten. Notches made for pipes or cablesshall also observe the 10 mm rule.

In case a floor continues under thethreshold, it is recommended to establish a20 mm joint between floorboards andbetween joists under the threshold, seefigure 44.

The use of chipboard or plywooddrastically increases the stiffness of thefloor as compared to floorboards. As a resultthe sound diffusion from the floor plane willbe increased and the impact sound insurrounding rooms will increase as will alsothe drum sound effect in the room inquestion. It is difficult to reduce the drumsound effect in rooms with wooden floors.Some reduction may be achieved byinserting mineral wool or sand in the cavitybetween the battens/joists.

38 ASPECTS RELATED TO SOUND

Guidelines for the use of woodenfloors in wet rooms

The wet room shall have an approvedand completed floor, i.e. inclusive afloor covering made of PVC or ceramictiles.Wooden floors are only allowed inimpact class L (low) with few baths perday and of short duration and efficientventilation after use. Low impact class isparticularly found in single familyhoses, holiday cottages and the like, cf.B&B-Direction 200 Wet roomsThe wooden floor must have a plainunderside with as few cavities aspossible along T&G joints and theboards should not be supplied with stressgrooves on the underside.The wooden floor is full-face glued tothe underlay in such a way that cavities,which may contain water, are eliminated.In order to prevent the penetration ofwater, all joints between boards andalong adjoining walls are caulked with amastic caulking compound.The joints must be inspected at regularintervals and repaired in case leaks aredetected.Wooden floor and materials used -including adhesives, caulkingcompounds and underlay - must becompatible.A distance of minimum 500 mmbetween the floor and shower stall, bathtub and floor drain must be observed,see figure 42.No pipe penetrations or floor drains areaccepted in the wooden floor (neither isit possible as no flor drains have beenapproved for the use in wooden floors)see figure 43.Accepted species are teak and specieswith similar characteristics in terms ofresistance and durability when exposedto moisture.Good heating and efficient ventilation isrequired in order to keep the room asdry as possible and thereby prevent theattack of fungi.

Floating floorsFloating floors with an elastic intermediatelayer in the form of an insulation materialwill reduce the impact sound level.The thickness and the elasticity(compressibility) of the layer greatlyinfluences the potential impact soundreduction. Large thickness and largecompressibility give high impact soundreduction.

The use of thin insulation below 10mm requires a completely levelsubstrate. Roughness in the underlaycaused for example by a pointed concretesurface may be pressed into the insulatinglayer and may cause contact between thefloor and the underlay, hereby increasingthe risk of sound bridges, see figure 45. Thefloors must not touch the surrounding wallsor pipes penetrating the floor.

The efficient sound reduction in floatingfloors very much depends on correctconstrution. For further informationconcerning sound insulation reference ismade to SBI-direction 172, Soundinsulation in buildings - newer buildingsand to SBI-direction 173, Sound insulationin buildings - older buildings.

Figure 44 Construction details ensuring impactsound reduction in floors on battens.

The latter also discusses possibilities ofimproving sound insulation in old storeypartitions by adding supplementary floorcoverings on top of existing coverings.

Figure 45 Construction details impact soundreduction in floating floors.

ASPECTS RELATED TO SOUND 39

Minimum 20 mmMinimum10 mm fromwall Insulated joint

under threshold

Minimum. 10mm above pipesSoft blocks

InsulationBatten

Minimum 10 mmclearance aroundpipes

Minimum 10 mmclearance

Minimum 10 mmfrom wall

Intermediate layerreducing impact sound

Wooden floor

Sub floor

Risk of sound bridges caused by pointed concrete

JOINTS

The purpose of establishing joints inwooden floors is: 1) to absorb expansions,2) to transfer forces and 3) to establish acharacteristic subdivision of the floorsurface.

Differentiation is made between dilatationjoints and insulation joints see figure 46.The purpose of dilatation joints is to absorbmoisture and temperature causedmovements between materials in the floorplane, figures 48-49. Dilatation joints arenormally only found in floating floors.Suspended floors on battens or on joists aswell as glued or nailed floors do notnormally require dilatation joints, providedthey are constructed correctly.

Insulation joints are used to separatefloors from adjacent building componentssuch as columns and walls, see figure 50.Insulation joints may function as dilatationjoints at the same time.

Joints shall be so designed that they arecapable of absorbing such movements asmay be expected in the floor plane inquestion. The number and position of jointsare determined by type of floorconstruction, load and expected moisturevariations as well as geometry of the roomand the wood species used.

In case dilatation joints have beenestablished in the sub floor, such joints mustbe repeated in the finished floor itself.

Mastic caulking compounds and softsynthetic rubber profiles are used forsmaller joints. Metal profiles are primarilyused when excessive movements areexpected in the floor plane.

Floating floorsLarge mechanic loads, for example frombook cases or reception desks in open spaceoffices may impede the movements offloating floors, see figure 46. This fact mayreduce the size of floor areas constructedwithout joints. The use of hard and strongjoints against adjacent floors or buildingcomponents may hamper the free movementof the floor plane.

Figure 46 The placing of dilatation and insulationjoints in floating floors.

Areas where large movements may beexpected, as a consequence of moisturevariations, require several wide joints ofhigh quality. Movements must not behampered in floors with irregular geometryand with columns penetrating the floor, seefigure 46.

Subdivision of the floor plane should, asfar as possible, be carried out in rectangularfields in order to allow for equal size ofexpected movements in both directions.Under normal circumstances it is possible toconstruct floor planes without joints up to8x12 m, where 12 m is the longitudinaldirection of floorboards. When constructinglarger floors it is advisable to consult thefloor manufacturer.

End grain wood block floorsExpected moisture related movements inend grain wood block floors is greater thanin most other wood floors. Reference ismade to the guidelines issued by the floormanufacturer concerning field sizes. Suchguidelines should be observed.

40 JOINTS

Dilatation joint

Dilatation joint

Dilatation joint Insulation jointaround column

Dilatation jointbetween columns

Dilatation joint

Insulation jointaround heavy fixedfurniture

Dilatation joint

Joints and caulking compoundsElastic polysulphide-, MS-polymers - orpolyurethane compound are used inwooden floors. With respect tocompressibility and wear the compoundsmust have a hardness corresponding to40-65° Shore A. In joints along wall a moreflexible compound is used. In order toavoid the adherence to the bottom of thejoint it is required to use slip tape, seefigure 47. Caulking compounds indilatation - and insulation joints mustalways be supported from below, seefigures 48-50. Therefore never caulkjoints without backing.

The width of the joint should be minimum8 mm and maximum 15mm. Along wall,columns etc. the joints may have a width upto 30 mm.

In as far as it is possible, the cross sectionof the joint should be square. When usingthick floorboards this may requireadjustment of the joint depth for example bythe insertion of pressure resistant, acid freecardboard EPDM profiles or polyesterneedle felt, see figures 47 and 50.

Documentation showing compatibilitybetween applied caulking compound andwood species must be available. This isparticularly important when using speciescontaining oil, for example teak. In suchcases the supplier s instructions concerningpriming must be followed carefully becausethe extraction of oil and resin from thewood may cause the forming of blisters inthe caulk.

Figure 48-50 Dilatation and insulation jointsshall always have support from below, forexample by the use of a metal bar serving as aloose tongue between to floor planes (49) or aloose batten under floors on battens (48 and 50).

Documentation must also be madeavailable on the compatibility between oil,varnish and other remedies for surfacetreatment.

Joints must be carried out inconsultation with the supplier of thecaulking compound in order to ensurecorrect choice of compound and primer. Asa rule of thumb all adhering surfaces mustbe cleaned and primed according tosupplier s directions. The caulk groovemust have clear cut and sharp edges. .Wooden surfaces bordering the joint must becovered with tape before caulking.

Floor which requires sanding may besanded with course sandpaper beforecaulking. Fine sanding takes place when thecaulking is hardened and after removal ofexcessive compound (by cutting).

For further information, reference is madeto guidelines issued by FSO.

JOINTS 41

Possible adjustmentof joint depth

Caulking compound

Caulking compound Caulking compound-Slip tape-

Loose metal tongue -Joint support for example aloose batten

Floor batten

Adjustment ofjoint depth

Figure 47 Placing of bottom stop, for exampleslip tape. The joint depth should be adjusted inorder to establish a square caulk profile.

Caulkingcompound

Caulkingcompound

Slip tape

Adjustment of jointdepth

Movement profilesJoints designed with metal profiles orextruded rubber profiles are used in areaswhere large movements are expected orwhere adherence between the materials onthe two sides of the joints is not acceptedsee figure 52.

A movement profile can be made withmetal anchoring legs (for examplealuminium) connected to a movement zonemade of soft synthetic rubber as shown infigure 52. Such profiles are available forwood / wood joints and for wood joiningother flooring materials. Special designsalso exist for the joining of floors withdifferent height levels. The profiles areproduced in a number of special designs,for example with angles for corners and inT-shape. The EPDM rubber profiles arealso produced in a number of differentdesigns, for example angle corners or T-shapes. The rubber is normally renewable.

Figure 51 Open joints covered with metal profile(cover strip). Is applicable to all floor types, seemore details in section Laying guidelines (page58)

Movement profile withvisible anchoring legs

Always use metal profiles or extrudedrubber profiles where the freemovement of the floor is desirable

Movement profile withconcealed anchoring legs

Ships plank joint / groove for filletShips planks are made by moulding a groovenext to the tongue on the top side of theboards. The groove is filled with a contrastmaterial in order resemble the originalcaulking. This contrast material can be acaulking compound, a wooden fillet, or arubber fillet, see figure 53. Ships plankjoints can also be established by theinsertion of loose fillets between the boardssee figure 49.

When ships plank joints are made using acaulking compound it is important to noticethat the cross section should be squaresimilar to other joint between floorboards.Bottom stop and priming is also important.Course sanding of the floor takes placebefore caulking, and fine sanding only takesplace after proper hardening of the caulkingcompound.

When ships plank joints are made usingwood or rubber fillets, the fillets are placedin the moulded groove where they aremechanically fixed and / or glued in aspecially created key. Wood fillets areglued with water resistant PVA-glue.Rubber fillets should be glued with glues asspecified by the supplier. Rubber filletsmay be joined at ends using cyanoacrylateglue (10-seconds glue).

Figure 52 Top: Visible standard profile fixedfrom above. Best solution for dilatation joint inglued / screwed floors.

Bottom: Concealed standard profile anchored tothe sub floor before laying the wooden floor. Theprofile is countersunk into the subfloor in order toestablish a plane surface.

42 JOINTS

Metal cover strip Metal cover strip

Figure 53Examples of grooves using caulkingand loose fillet

LAYINGINSTRUCTIONS

The choice of underlay for wooden floorsshall be adjusted to the type of floor inquestion and shall always be sufficientlyrigid and plane in order to ensure the correctlaying of the wooden floor.

CoveringUnder normal circumstances a woodenfloor should always be covered immediatelyafter laying in order to protect the flooragainst damages during the remainingconstruction period. Materials used forcovering could be cardboard or woodenfibre boards.

Areas with much traffic, door steps andstaicases, which are particularly vulnerable,should always be covered with cardboardor hard wood fibre boards. The wood fibreboards are fixed by taping to theunderlaying cardboard using an appropriatetape in order to avoid the undesiredentering of dust and dirt particles under thecovering, where such particles may causedents and scratches in the finished floor. Ondoor steps and staicases the fibre boardsmay be fixed using small pins along edges.

Wooden floors on battens or joistsFloors on battens are normally laid on asubstrate of concrete or light weight concrete,but may also be constructed on top of awooden sub floor. When laid on concrete it isrecommended always to lay a dpc beforelaying the floor in order to avoid problemsoriginating from the presence of constructionmoisture or from capillary rise of groundmoisture. The dpc could for example beminimum 0.20 mm PE-foil laid withminimum 200 mm overlap at joints.

Distances between supportsThe support distances for suspended floorson battens are indicated in tables 4 and 5.The distances indicated ensure a reasonablystiff floor preventing annoying vibrationswhen walking and preventing theinconvenient inclination of furniture andequipment caused by floor deflection. Thesupport distance depends on the chosenthickness of materials and the expectedload, see figure 54.

Figure 54 Batten or joist distances as well asblocking-up distances are measured form centre tocentre (c/c)

The laying of battensAs a minimum requirement, the battensshould be planed and straightened on oneside and be in one piece.

The first row of battens is placed at adistance of 50-80 mm from the wall. Alongwalls, where heavy loads normally occur, extrabattens are placed as shown in figure 55(unless otherwise instructed by themanufacturer). The battens are placed with thedesired distance and chocked with blocks,wedges or similar packing pieces in order toadjust the height, establishing a plane surfaceacross the battens. Packing pieces must rest ona plane surface in order to secure stability.

Figure 55 Placing of battens. Notice the extra battenalong walls and the staggered packing of battens.

FLOORS ON BATTENS 43

Extra batten approx. 70 cm

Packing piece

Extra batten

* Guiding values

Wooden based blocks used as packingpieces should always be glued together inorder to avoid displacement. The packingpiece material should be fixed to the battenwith a nail in order to avoid displacementduring the laying and later during the use ofthe floor. The fixing also helps preventingsqueaking floors. The usual nailing methodis toe-nailing , i.e. a nail entering thebatten on the side and continuing at anangle into the block or wedge, see figure 56.

When soft blocks are used with thepurpose of sound reduction, care must betaken to ensure that the nail does not enterthe soft material, see figure 57. The densityof the soft wood fibre board shall be 225-300 kg/m3 and the size shall be minimum100 cm2, for example 100 x 100 mm in orderto avoid settlement in the floor when loadsare applied. The plywood block placed ontop must have the same dimension, seefigure 57.

In basement floors and on groundsupported floors extra care must be taken inorder to avoid the absorption of moisture. Itis therefore recommended to place a piece ofbitumen felt (200 x 200 mm) below thepacking pieces.

Figure 56 The packing of battens using wedges

44 FLOORS ON BATTENS

Floor material Batten or joist distanceMinimum thickness in mm Dwellings etc. Smaller shops Assembly rooms or the likeFloorboards20 mm tongued and grooved boards 520 420 36022 mm tongued and grooved boards 600 490 42025 mm tongued and grooved boards 720 590 50028 mm tongued and grooved boards 860 700 60030 mm tongued and grooved boards 950 770 670Structural sub floors*15 mm Plywood glued in T&G 400 350 32018 mm Plywood glued in T&G 600 520 48022 mm Flooring chip board glued in T&G 600 520 480

Toe-nail

Wedges

Possibly bitumenfelt 200x200 mm

Plywood packingpiece 100x100 mm

Toe-nail

Table 4 Batten and structural joist distances calculated from centre to centre The distances ensureagainst undesired deflection and vibrations. When a calculation indicates a dimension somewhere inbetween the indicated distances, the nearest lower distance should be applied.

Wooden floor

Batten

Batten

Figure 57 Chocking-up battens using wooden blockpacking pieces and posiibly bitumen felt. When softblocks are used with the purpose of sound reduction,care must be taken to ensure that the nail does notenter the soft material

Soft boardpacking piece100x100 mm

Wooden floor

Floor on battens

Figure 59 Packing of battens by the use of highplastic wedges creates sufficient space for therunning of pipes.

Figure 58 When packing battens on a woodenstorey partition the position of the packing piecesmust be aligned and in line with structural joistsbelow and comply with distances indicated in table4. When battens are positioned perpendicularly tostructural joists, it is required to choose a battendimension which allows for a chocking-updistance at least corresponding to the distancebetween the structural joists.

Chocking-up on top of structural joists isshown in figure 58. The overall height ofthe packing pieces must allow for a gap ofminimum 10 mm between batten andunderlay. In case pipes or other installationsare placed under the floor, there must be atleast 10 mm between such installations andthe batten.

Pipes under the floor shall be well-insulated in order to avoid the undesiredheating of the wooden floor, see figure 59.

In case incisions are made in the battens,it is required to establish an additionalsupport on either side of the incision, seefigure 60.

Battens shall always be supported at buttjoints (end joints), see figure 61. Butt jointsmust not be aligned under the samefloorboard.

Figure 60 When incisions are made in thebattens, for example for pipes, it is required toestablish additional supports on either side ofthe incision.

FLOORS ON BATTENS 45

Toe-nail Toe-nailPlywood packing Insulated pipeSoft board packing

Plastic wedges

Possibly dpcWooden joist/woodenstringer

Wooden deck element orwooden storey partition

Batten Insulated pipe

Incision

Soft block

Minimum10 mmdistanceto batten

Wooden floorBatten

In renovation work, where it may beimpossible to avoid the aligning of buttjoints, it is required to reinforce the jointswith fishplates on either side of the joint,using for example 12 mm plywoodfishplates minimum 300 mm long. Thequality of the plywood used must, as aminimum, correspond to American C-D orbetter.

When joints are made without the use offishplates it is required to support each endof adjoining battens using packing pieceswith a minimum length of 125 mm(measured along battens). The packingpieces are placed roughly 50 mm from theends of the battens see, figure 61.

The distance between packed basesdepends on batten dimension, as shown intable 5. The spacing between packed basesshall be reduced at batten ends and battenjoints, see figure 62.

When, in exceptional cases, stress reliefcuts are established, it is required to placepacked bases under each such cut and thespacing between bases shall be reducedaccording to figure 62.

Spacing of packed bases andBattens used as underlay for wooden floorsshall be sufficiently stiff in order to ensurethat it feels safe to walk on the floor.

Table 5 shows the normal spacingbetween packed bases (lmax in mm) for anumber of cross sectional dimensions andtypes of battens

The spacing shall be reduced by at least10 % along batten ends. This also applies tobattens butt joints and possible stress reliefcuts, see figure 62.

In dwellings, offices and light industrythe point load Q is set to 2 kN, for smallershops Q equals 3 kN, and for assemblyrooms and bigger shops Q is set to 4kN.

The spacing between supports andpacked bases indicated in tables 4 and 5may be used in normal rooms according tomentioned user classes. In cases where thefloor is temporarily exposed to loadsexceeding the loads normally occurring inthe user class in question, it is required toreduce the distance between supports andpacked bases in accordance with theexpected extra load, for example fromelectric wheelchairs, trucks and heavybook cases.

The spacing between packed basesis reduced by minimum 10 % atbatten ends.

Figure 62 The distance between packed bases shallbe reduced at batten ends, at batten joints and wherestress relief grooves are established. The reductionnormally corresponds to 10 % of normal spacing.

46 FLOORS ON BATTENS

Fishplates minimum300 mm

Maximum 100 mm

Figure 61 An additional support shall always beestablished when battens are butt jointed orjoined with fishplates.

Spacing betweenpacked bases

÷ 10 %

Table 5 Spacing of packing pieces and cradle systems under floor battens in main floor area. Along ends ofbattens the spacing shall be reduced by 10 %, see figure 62. Design assumptions for table 5 are described onpage 48.

Batten Dwellings, offices anddimension light industriesheight x width (Q = 2 kN)mm Sawn Laminated

battens1 battens2

Smaller shops

(Q = 3 kN)Sawn Laminatedbattens1 battens2

Assembly rooms andlarger shops(Q = 4 kN) ____________Sawn Laminatedbattens1 battens2

1 The indicated distance is allowed provided the wood used has a stiffness corresponding to K18 (E0 = 9000MPa)

2 The indicated distance is allowed provided the laminated wood used corresponds to L30 (E0 = 12000 MPa)or to L40 (E0 = 14000 MPa). The stiffness in laminated products depends on number of layers, wood qualityand production method. Supplier will inform about Elasticity module upon request.

3 Sawn battens produced from solid coniferous wood and graded in accordance with grading class T1 willcomply with strength class K18 requirements.

4 Laminated battens produced (glued together) from planed coniferous staves will normally achievestrength/stiffness properties equivalent to strength class L30.

5Laminated battens type LVL (Kerto and others) normally have) v strength/stiffness properties equivalent tostrength class L40.

FLOORS ON BATTENS 47

The laying of floorboards nailed orscrewed.Before laying the floor it is required to packbatten supports in order to establish a levelsurface across the battens. This is controlledby the use of a straightedge and a spiritlevel or by laser levelling, see figure 63.The first row of boards is laid with thegroove facing the wall. The boards arealigned using a building line. A clearance of

minimum 10 mm between wall andfloorboard must be observed. In largerrooms it is necessary to increase the distance,depending on room dimensions and floorproduct in accordance with manufacturer sinstructions.

Temporary distance blocks are placedbetween the first row of boards and the wallin order to avoid the displacement of theboard during the laying process, see figure63.

48 FLOORS ON BATTENS

Design assumptions used in the calculation of spacing between packed basesand other supports under floor battens:

Maximum support distance lmax for supportsunder central part of a batten with thewidth b, the height h and the effective E-module Es and exposed to point load Q canbe determined by the use of this formula:lmax

3= l0mm bh3Es/QThe distance is rounded off to whole 10mm units. Along ends, and in rare cases ofstress relief cuts in battens, it is required toreduce the support distance by 10 %.

The constant 10 mm has been chosen insuch a way that lmax becomes 600 mmfor a sawn batten with cross sectionaldimensions of 45x45 mm and normalstiffness Eo = 9000 MPa (Structuraltimber class K18).

Table 5 shows the support distances for anumber of cross sectional dimensions andcode stiffness with maximum supportdistance lmax in central floor area as afunction of point load, wood quality andbatten dimension. In dwellings, officesand light industry the point load Q = 2kN,in smaller shops Q = 3 kN and in assemblyrooms and larger shops Q = 4 kN.

It should be noticed that battens are notpart of the load bearing structure and assuch are not subject to code requirements.Consequently, it is irrelevant whethercalculations show whether or not thebattens will be able to accept assumedpoint loads in DS 410:1998.

Battens used as underlay for wooden floorsshall be sufficiently stiff in order to ensurethat it feels safe to walk on the floor.The below mentioned formulas describe theacceptable distances between batten supportsdepending on load, cross sectionaldimensions and wood quality (E-module).The formulas are defined on the basis oftraditional norms, but adjusted to loads andstiffness requirements listed in DS 410:1998Code of Practice for Loads for the Design ofStructures and in DS 413:1998. Code ofPractice for the structural use of timber

The code values for point loads and surfaceloads in different user classes (for exampledwellings, offices, assembly rooms) areassumed to represent the correct mutualrelationship between loads. In practice, theonly factor of real interest is the deflectioncaused by the point load.

The stiffness of normal structural timber isusually much higher than the mean valueEo stated in DS 413. In order to achieveuniform stiffness in battens made oftraditional structural timber and in battensmade of processed materials with apredefined stiffness, the effective E-moduleused in the following will be defined as:Es = 12000Eo MPa for Eo < 12000 MpaEs = Eo for Eo 12000 MPa

Figure 63 The battens must be completely level and stable. The boards are aligned using a building lineand clearance is established along walls.

Floorboards nailed / screwed from above.When boards are fixed using visiblenailing /screwing, the nail / screw is placedat a distance corresponding to ¼ of theboard width from the grooved edge of theboard. When boards are particularly wide,i.e. more than 200 mm, the visible nailing/screwing requires two nails / screws inevery board, see figure 64.

In the case of secret fixing from above,the boards are fixed using countersunkwood screws. Screw holes are pluggedwith wooden plugs, see page 19. Otherwisethe floor is laid in accordance withguidelines applying to floors with secretnailing / screwing.

Figure 64 Floorboards - screwed / nailed from above.In case the boards are wider than 200 mm it is requiredto use two screws / nails according to distancesindicated.

FLOORS ON BATTENS 49

Distance blocks

Tongue

Groove

Tongue Groove

Straightedge

Batten

Extra batten

Extra batten Dpm - optional

Min. 50 mm

Distance blocks,minimum 10 mm

Batten

Floorboards with secret nailingFloorboards may be fixed using secretnailing or secret screwing. When boards arescrewed, pre-drilling is always required.

The first board is nailed to the batten fromabove using secret nailing in the tongue, seefigure 65. The visible nail in the first boardis places roughly 20 mm from the groovedside of the board. Finishing nails are driveninto the wood with a nail set, and the holesare filled with adequate filler.

The tongue side is fixed using secretnailing from the upper side of the tongue.The nails are placed at an angle roughly 45-60° in relation to the upper side of thefloorboard. Nails are driven into the wood.It may be necessary to pre-drill in order toavoid damaging the tongue, see figure 66.er

It is recommended to blunt the nail point inorder to avoid splitting of the wood. Thehead of the nail may be used to drive in theprevious nail. Doing so, the nail headbecomes slightly rectangular. Placing thelong side of the nail head parallel to theboard will reduce the risk of splitting.

Guiding dimensions for nails areindicated in table 2, page 17. Boards arenailed in all battens. However, it is notrecommended to nail at a distance shorterthan 50 mm from the end of a board, seefigure 64.

Subsequent boards are laid and knockedtogether using a hammering block or ahammering rail making observing the 10-board measurement, see figure 67. In somecases a board oof-cut may be used ashammering block. In other cases it isrequired to use a special hammering blockin order to avoid damaging the profile.

Figure 65 Fixing the first board and nailingprinciples in remaining boards.

Figure67 The boards are knocked together usinga hammering block or a hammering rail.

Figure 66 Placing and dimensions of nailswhen nailing through the tongue (secretnailing).

Cupped and warped boards can be difficultto force in place alone by nailing. The useof wedges as shown on figure 68 may helpsolving this problem forcing the board intoplace. Clean-cut board ends must be joinedalong batten centreline. Butt jointed boardsshould have the same orientation of annularrings in order to avoid the cupping inopposite directions when the boards dry out,see figure 69. Boards are square cut in orderto ensure a tight joint. In order to furthersecure a tight joint both cuts may haveslight inclination away from the joint, seefigure 69.

50 FLOORS ON BATTENS

Hammering block

2.8x65 mm3.1x80 mm3.4x90 mm3.4x90 mm

Floor board Batten

Packing pieces

Figure 68 Curved boards may be forced in placeby the use of wedges.

Figure 70 Butt jointed boards must span acrossminimum 2 bays. Not more than every third boardshould be joined on the same batten.

Avoid differentorientation ofannular rings

Figure 69 Butt jointed boards must have similarorientation of annular rings, and it is an advantageto bevel the cut slightly in order to establish atight joint.

Figure 71 Boards with T&G unsupported buttjoints may be used in dwellings or similar.Unsupported joints must not be used in first andlast board and not in more than every third boardwithin the same bay never in neighbouring bays.

Boards and joints of this type must spanacross two bays at least, and not more thanevery third board should be joined on thesame batten, see figure 70.

Boards supplied with T&G in the endsmay be joined without support frombeneath, so-called unsupported butt joints.This type of joints must always be glued.When using boards with T&G unsupportedbutt joints, the laying is continued using theoff-cut from the previous row as starterpiece in subsequent row.

End joints within the same bay may onlyoccur in every third board, i.e. there mustbe two continuous boards between everyunsupported butt joint, see figure 71.Unsupported butt joints must not occur inneighbouring bays, and no unsupportedbutt joints may occur in the first and thelast row. Unsupported butt joints shouldnot be used in floors exposed to loadsexceeding those occurring in dwellings.

FLOORS ON BATTENS 51

Wedges

Woodenblock fixedto batten withscrews

Batten or joist

Bevelled cut

Butt joint along battencentreline

Board

2 bays Board

No unsupported joints

Unsupportedbutt jointswith T&G endjoints

No unsupported joints 2 bays between buttjoints

The last board is designed as shown infigure 72. It is sometimes difficult to fit inthe last board, and to solve this problem itmay be expedient to chamfer the upper lipof the groove on the side facing the centreof the board. It is also possible to bevel theside of the board facing the wall. In case thelast board is very narrow it may benecessary to lay the last two boardssimultaneously. They are glue-jointed beforethe laying, see figure 73.

In case the supplier recommendsobservation of the 10-board measurement itis required to comply with the saidmeasurement. The 10-board measurementindicates the cover width of 10 boards. The10-board measurement is indicated as aninterval, for example 1293 1298 mmwithin which random check measures of thewidth of 10 boards must fall.

Figure 74 Door with threshold and floorboardsperpendicular relative to door opening. Noticemaximum joist distance.

Figure 72 Designing the last board.

The last two boardscan be glued /nailed together.

Figure 73 Laying the special-made last board.

Figure 75 Packing of threshold floors withdifferent levels.

The measurement depends on the width ofthe individual boards, the expected highesthumidity during use, and the chosen woodspecies.

Doors with thresholdThe floorboards meet under the threshold.There should be a clearance of 20 30 mmbetween ends of floorboards in the dooropening depending on extend ofadjoining floors. When boards are placedperpendicular to door opening, as shownin figure 74, the joints between the

52 FLOORS ON BATTENS

Maximum. 250 mm

Packing

Wedge-

Figure 76 Floorboards may continue throughdoor openings when the door has no threshold.This solution should only be used in smallerrooms.

Figure 77 Joint covered with metal strip. Thissolution is used when floorboards are positionedperpendicularly or parallel in relation to each other.

boards should be aligned on either side ofthe threshold. The floor planes inadjoining rooms should have the samelevel. In case this is not possible, thethreshold should be packed in order toalign it with the level of the highest floor,see figure 75.

Doors without a thresholdIn case the doors do not have a threshold it ispossible to let floorboards continue throughthe door opening when the floorboards arepositioned perpendicularly relative to theopening, see figure 76.

When floorboards continue through adoor opening it is required to design thewidth of the joints along walls as if the floorwere in one room, measuring the widthfrom wall to wall through the door opening.

When floorboards in one room arepositioned perpendicularly relative tofloorboards in adjacent room, as shown infigure 77, it is required to establish a jointwith between the two floors. The width ofthe joint should be 15-20 mm depending onthe size of adjoining floors. If needed, thejoint may be covered with a flat or curvedmetal cover strip. The strip should only befixed to one of the floors and must not becountersunk to become flush with the floorsurface.

This solution may also be applied incases where the floorboards in both roomsare positioned parallel to the dooropening. In this case the joint will acceptmovements from both floor planes.

Pipe penetrationsHoles for pipes shall have a diameter 20mm larger than the pipe going through thehole in order to allow for the independentmovement of the floor, and in order toensure that there is no contact betweenfloor and pipe.

When floors are fitted after pipeinstallation the hole is cut as illustrated infigure 78. Once the floorboard is in placethe cut out block is glued back intoposition, and the hole is covered with anescutcheon.

Figure 78 Cutting a hole for pipe penetration. Thewedge has bevelled sides ensuring a tight fit in theopening.

FLOORS ON BATTENS 53

Metal cover strip

Wedge withbevelledsides

Floating floorsFloating floors are normally laid on structuralfloors made of concrete, lightweight concreteor wood. When laid on concrete orlightweight concrete it is recommendedalways to lay a moisture barrier in order toavoid construction moisture or groundmoisture from entering the floor. Themoisture barrier should consist of minimum0.20 mm PE-foil laid with minimum 200mm overlap in all joints. In case it isrequired to lay the wood floor very soonafter casting the concrete it is required touse a very tight moisture barrier, forexample bitumen felt glued to the concreteslab and with airtight joints, see Gluingbitumen felt, page 21.

Underlay and intermediate layerBefore laying intermediate layers it isrequired to level the sub floor creating aplane surface, for example by the use of asmoothing compound. Deviations fromplaneness should be less than ± 2 mm whencompared to a 2 m straightedge.

Type of intermediate layer is chosen withconsideration to establishing a reasonablyrigid floor which does not shakeunnecessarily when walked on, and does notcause the inclination of furniture orequipment due to deflection. Maximumdeflection should not be more than be 2.5mm.

The preferred materials for intermediatelayers are: Expanded polystyrene typeEPS 150 or EPS 250, hard mineral woolbatts, porous wood fibre boards, robust geotextile in more the one layer, foam plasticsheets with air bubbles and special matsbased on rubber and cork. When usingcompressible intermediate layers likemineral wool and polystyrene, it isrecommended to insert a pressuredistributing board, for example 22 mmfloor chipboard.

The floor planeFloating floors are made in such a way that thefloor constitutes one coherent floor plane ableto move independently in relation to theunderlay. The floor plane may be constructed

with coherent wood or concrete sub floors ontop of which the wood floor is laid out andmaybe glued. The sub floor has a pressuredistributing function and, being so, the floorcovering does not need to be a suspendedfloor, but can be made of short block parquetor mosaic parquet, see figures 79-83

Figure 79 Floating floor constructed with parquetblocks or parquet boards glued onto a woodflooring panel laid on a thin intermediate layer

Figure 80 Floating floor constructed with parquetblocks or parquet boards glued onto a woodflooring panel which again is laid on hardinsulation.

54 FLOORS ON BATTENS

Wood floorGlue

Wood flooring panel

Moisturebarrier

Intermediatelayer

Concrete

Wood floorGlue

Wood flooring panel

Moisturebarrier

Hardinsulation

Concrete

Figure 81 Wooden floor glued on top of a floatingconcrete slab. Notice that the concrete slab mustbe completely dry and plane before gluing thewood floor.

Figure 83 Floating floor made with pressuredistributing flooring panels laid on top of hardinsulation. The floor cover is T&G floorboardsjoined with steel clips and laid on a thinintermediate layer in order to reduce clattering.

Figure 82 Floating floor made with pressuredistributing flooring panels laid on top of hardinsulation, The wooden floor (glue-joined woodveneer floorboards) is laid on a thin intermediatelayer in order to reduce clattering.

Figure 84 Floating floor made with glue-joinedwood veneer floorboards laid on a rigidunderlay, for example concrete, and with a thinintermediate layer, which may function as asound reducing layer and as a moisture barrier atthe same time.

Floating floors may also be constructed bythe use of wood vceneer floorboards orsimilar laid on a rigid substrate. The boardsare placed on top of a thin sliding layer, forexampe a 0.20 mm PE-foil and/or a corksheet placed on the rigid underlay. The ri-

gid underlay could be a concrete slab, awooden sub-floor made of flooring panelslaid on battens or joists etc. The boards arejoined either by gluing in the T&G accordingto manufacturer s instructions or by the useof purpose-made clips placed in grooves onthe backside of the boards, see figures 84-85.

FLOATING FLOORS 55

Glue Wood floorConcrete slab

T&G floorboards joined with steel clipsIntermediate layer

Wood flooringpanel

Moisturebarrier

Hard insulation

Concrete

Hard insulationMoisturebarrier

Concrete

Intermediate layerWood floor

Wood flooring panel

Moisturebarrier

Hard insulation

Concrete

Wood floorIntermediate layer

Moisturebarrier

Concrete

It is required to supply planks and flooringpanels with T&G on all four sides in orderto use them as floating floors placed directlyon top of an intermediate layer.

Flooring panels used as sub-floors mustcarry a marking stating approval for use infloor constructions.

The floor plane must not be fixed, i.e.should be able to move freely. It isimportant to observe that there shall be adistance of minimum 10 mm between floorand all surrounding walls and aroundpenetrating installations, for example pipes.This distance depends on the size of thefloor and the manufacturer srecommendations should always befollowed.

In order to prevent the floor fromcracking it is normal procedure to establishdilatation joints at every 8 m across thewidth of the floor (measuredperpendicularly to grain direction in thewood). It is also recommended to establishdilatations joints in floating floors subjectto heavy loads, as for example in officeswith heavy filing cabinets, because the loadmay prevent the floor from moving freely.In case dilatations joints are notestablished the result may be cracks andchinks in the floor. The floor may also crackin case the room is very irregular and in thisway hindering the free movement of thefloor.

Laying a floating floorThe laying instructions described below referto plank floors in the form of floorboards,wood veneer floorboards and the like. Forthe laying of parquet blocks, parquet tiles orblocks on a floating sub-floor, reference ismade to the subsequent section about gluedand nailed floors.

The first row of boards is laid with thegroove facing the wall. The boards arealigned by the use of a building line. Adistance of minimum 10 mm between thewall and the board must be established. Inrooms exceeding 6 m - measured across thegrain direction in the wood - and 12 m alongthe grain direction, the distance shall beincreased in accordance with roomdimension and wood species. Temporarydistance blocks are placed between the firstrow of boards and the wall in order toensure that the boards are not displacedduring the laying, see figure 86.

Figure 86 Laying the first row of boards with thegroove facing the wall and held in position bytemporary distance blocks.

Figure 85 Floating floor carried out withfloorboards joined with clips and laid on a rigidunderlay, for example concrete. A thinintermediate layer which may function as a soundreducing layer and as a moisture barrier at thesame time is introduced between floor andunderlay.

The next row of boards is now placed and theboards are knocked together using ahammering block or a hammering rail. Insome cases the hammering block may simplyconsist of a sawn off piece of board, whereasother products may require the use of aspecial hammering block in order to avoiddamaging the profile (the tongue side of theboard)

56 FLOATING FLOORS

T&G floorboards joined with steel clips

Intermediatelayer

Moisturebarrier

Concrete

Distance blocks

TongueGroove

Intermediatelayer

The boards are joined by gluing the T&G orby the use of clips. When joining boardsend-to-end, the T&G must also be glued.The laying continues using the cut-off froma previous row as the starting board in thenext row. Using this principle, the end-to-end joints of the boards will be staggered.End-to-end joints in two neighbouring rowsshall be staggered by minimum 500 mm, seefigure 87,

The last board is adapted as shown infigure 88. It may be difficult to fit in the lastboard. The process of fitting the last boardcan be made easier if the lower side theupper lip of the groove is chamfered.

Figure 89 Laying the last board(s)

Figure 90 The last board is knocked into place bythe use of a hammering rail or squeezed intoplace by the use of a crowbar.

Figure 87 Placing end-to-end joints of theboards. Avoid closely placed end-to-end jointsin neighbouring rows (zig-zag-pattern).

Figure 88 Tracing the size of the last board.

It is also possible to cut the edge of theboard at a slight inward angle on the sidefacing the wall. In case the last board is verynarrow it may be necessary to lay the lasttwo boards simultaneously. In this case theyshould be glue-joined before laying them,see figures 89-90.

In case the supplier recommends that thefloor is laid in accordance with the 10-boardmeasurement, it is required to observe themeasurement requirement indicated. The10-board measurement indicates how widean area 10 boards should cover. The 10-board measurement is indicated as aninterval, for example 1293-1298 mm, i.e.the covering width of 10 boards shall fallwithin this interval. The measurementdepends on: The width of the boards, theexpected highest air humidity and the floorproduct used.

FLOATING FLOORS 57

The last two boards my benailed/glued together. , Wedge-

Bevelled edge

Hammeringrail

Minimum 500 mm

Avoid uniform staggering of theboards

Doors with a thresholdThe floorboards extend under the threshold.It is required to establish a distance ofminimum 20-30 mm between the floorboardswhere they meet in the door opening depending on the sizes of the adjoining floors.In case the boards are perpendicular to thedoor opening, as shown in figure 91, thejoints between the boards should be alignedon the two sides of the threshold. The levelsof the floors in adjoing rooms should be thesame. In case this is not possible, the thresholdshould be packed to the level of the highestfloor, see figure 92.

Figure 91 Floating floor with boards perpendicular todoor opening doors with a threshold.

Doors without a thresholdIt is usual practice to establish a jointbetween the two floors where they meet inthe door opening in order to allow formovements caused by humidity changes.The joint can be concealed by the use of aflat or curved metal cover strip fixed inone of the floors only, see figure 93. Thecover strip must not be countersunk intothe floor as this may prevent the freemovement of the floor.

Figure 93 It is usual practice to establish a jointbetween floor in adjoining rooms, in particularwhen the floorboards are perpendicular to eachother or when they are parallel to the dooropening.

Figure 92 Packing the threshold betweenfloating floors at different levels.

Figure 94 Where there is no threshold, thefloorboards may continue through the dooropening. It is, however, recommended to use thismethod in smaller rooms only.

58 FLOATING FLOORS

FtfstSpter-re

Wooden floor

Minimum 20 mm

Wooden floorCover strip

Wooden floor

Intermediate layer

Moisturebarrier

Concrete

Intermediate layer

Moisturebarrier

Wooden floorWooden floor

Wooden floor

Wooden floorPacking

Intermediate layer

Moisture barrierConcrete

Intermediate layer

Concrete

Moisturebarrier

Where there is no threshold, thefloorboards may continue through the dooropening, as shown in figure 94.

When boards run through the dooropening, it is required to dimension the jointalong the walls in both rooms as if the floorwere one floor with a total widthcorresponding to the width of both roomsmeasured through the door opening.

Pipe penetrationsAll holes for pipes shall have a diameter 20mm larger than the pipe going through thehole in order to allow for movements.

Around existing pipes it is possible to cutout a V-shaped block shown in figure 95.After placement of the board, the block isglued back into place and covered with apipe escutcheon.

Glued or nailed floorsA wide range of wooden floor materialsmay be laid either as glued floors or asnailed floors directly on a subfloor.

The subfloor shall be stable and rigid. Therequirements to evenness and flatness of thesubfloor are the same as requirementsapplying to the final floor. Deviations fromflatness shall be less than ± 2 mm measuredwith a 2 m straightedge, see Appendix:Flatness.

The subfloor must be without any leveldifferences and there must be no sharppoints. In case the requirements to flatnessare not fulfilled, it is required to adjust theflatness, for example by means of sanding orby the use of a filler compound.

Nailing/screwingAll wooden floors with a tongued andgrooved floorboards/blocks may be nailed orscrewed to the substrate provided thesubstrate is suitable for such fixing forexample a new subfloor made of particleboard or an existing wooden floor. Nail andscrew dimensions must be chosen inaccordance with board thickness, seeFasteners and adhesives. In case thesubfloor is made of particle board, it isrequired to use screws.

Fixing is normally carried out as secretfixing, i.e. by screwing or nailing at an angle -starting at the topside of the tongue (seefigures 97-98). The secret fixing of woodveneer floorboards with a core of particleboard must not be carried out withoutconsulting the manufacturer. On concretesubfloors, the fixing may be carried out byscrewing directly into the concrete - seeFasteners and adhesives.

The laying of floorboards screwing ornailing.The principles applied are similar to thoseprinciples described in the sectionconcerning floors on battens/joists.

The first row is laid with the groove facingthe wall. The boards are aligned by the use ofa building line. A minimum distance of 10mm must be observed between the boardand the wall.

In rooms with dimensions exceeding 6 mmeasured across the boards, and 12 malong the boards, it is required to increasethe distance between the boards and thewalls in accordance with room size.Temporary distance blocks are placedbetween the first row of boards and thewall in order to ensure that the boards arenot being displaced during the laying of theremaining part of the floor.

GLUED AND NAILED FLOORS 59

Concrete

Figure 95 Cutting out for a pipe. The V-shapedblock is glued back into place and covered with apipe escutcheon.

Intermediate layer

V-shaped block

Floorboards/screwed from top sideBoards fixed with visible nails/screws,should be fixed with a screw/nail placedapproximately ¼ board width from thegrooved edge of the board. Boards whichare particularly wide, i.e. 200 mm or more,are fixed with two visible nais/screws inevery board, see figure 96. It is possible toclose the nail/screw holes using woodenplugs.

Figure 96 Floorboards nailed or screwed from thetop side. In case the boards are more than 200 mmwide, they must be fixed with two screwsobserving the distances indicated.

Figure 98 Dimensions and placement ofscrews using secret fixing, for example onconcrete

Floorboards secret nailing/screwingThe first board is nailed from the top andalso secretly in the tongue, see figure 97.The visible nail in the first board is placedsome 20 mm from the grooved edge of theboard. Brads are countersunk with a nailpuncher, and holes are filled using anappropriate filler. The tongue side of theboard is nailed through the upper side of thetongue. Nails are placed at an anglebetween 45° and 60° in relation to theupper side of the board. Nails are punched.In some cases it may be advisable to pre-bore in order to avoid the splitting of thewood. A similar fixing may be carried outusing screws also when fixing toconcrete, see figure 98.

When nailing, it is important to blunt thepoint of the nail in order to avoid splitting ofthe wood. The head of the nail may be usedfor punching the previous nail. In this waythe head will be slightly flattened - obtainingan oblong shape narrow in one direction.

Figure 99 Boards are knocked together using ahammering block or a hammering rail.

60 GLUED AND NAILED FLOORS

Wood floor

Figure 97 Fixing of the first board and secretnailing of the remaining boards.

Distance blocksTongue

Groove

Min. 10 mm

Intermediate layer

TWood panel subfloor G

Hammering block

When nailing, the narrow edge of the nailhead should be kept parallel to the woodgrains. This will reduce the risk of splittingthe wood.

Nail dimension guidelines are shown intable 2 on page 17. Nails should be placedat least at every 600 mm, but nails shouldnever be placed closer than 50 mm from theend of the board, see figure 96.

Subsequent rows of boards should now belaid, and the boards are knocked together.The hammering block could be made of anoff-cut from one of the floorboards. In somecases it is required to use a specialhammering block in order to avoid damagingthe board profile (the tongue), see figure 99.

End joints of boards shall be glued in theT&G, but must never be glued in the T&Galong the sides of boards. The laying iscontinued in subsequent rows alwaysstarting a new row with the piece of boardleft over from the previous row. Doing so,the end joints between boards willautomatically be staggered. End joints intwo neighbouring rows should have adistance of minimum 500 mm, see figure100.

It may be difficult to fit in the last board,but the process can be made easier bychamfering the upper lip of the groove onthe last board. The board may also be cut atan angle on the side facing the wall. In casethe last board is very narrow it may berequired to fix the last two boards at thesame time. In this case they are gluedtogether before laying. See figures 101-102.

In case the supplier recommends layingthe floor in accordance with the 10-boardmeasurement, the covering width of 10boards must be stated. The 10 boardmeasurement is indicated as an interval, forexample 1293-1298 mm, indicating thetolerance of a random measurement acrossany 10 boards in the floor. Themeasurement depends on the width of theboards, the expected variation in airhumidity during use and the wood speciesused.

Figure 100 The placing of end joints. Avoid thetoo close placement of end joints in neighbouringrows (zig-zag-pattern).

Figure 101 Laying the last board

Figure 102 The last board is knocked into placeby the use of a hammering rail o it may be pressedinto place using a crow bar.

GLUED AND NAILED FLOORS 61

Minimum 500 mm

Avoid placing endjoints in neighbouringrows too close

The last two boards maybe glued/nailed together.limes/s0mmes sammen

Chamfered edgeWedge

Hammering rail

GluingWhen gluing it is important that surfaces areclean, dry and ready to accept glue, seeFasteners and adhesives.

Flooring materials must not be twisted andshall have a perfectly plane undersideensuring good bonding.

Parquet blocks without T&G shall have amaximum length of 300 mm. Parquetblocks with T&G shall have a maximumlength of 700 mm.

Solid wooden floorboards cannot normallybe glued to the substrate as it may bedifficult to ensure sufficient bondingthroughout the length of the board and alsobecause the moisture related movements inthe boards are greater than the elasticity ofthe glue.

Wood veneer floorboards should only beglued to the substrate in case themanufacturer recommends so - and provideslaying instructions for this method. It mustbe ensured that the glue has filling capacityand the the substrate is plane, (i.e.maximum +/- 2 mm deviation measuredalong a 2 m straightedge and +/- 0.6 mmwhen measured along a 0.25 straightedge)in order to secure good contact betweenglue and boards throughout the gluedsurface.

The laying procedure is similar toprocedure for nailed floors.

The first row is placed with the groove-side facing the wall. The blocks are alignedby the use of a building line. Minimum 10mm distance between floor and wall must beobserved.

In rooms larger than 6 m measured acrosswood grains and 12 m measured along thegrains, the distance to surrounding walls, orany other surface bordering the floor, mustbe increased depending on roomdimensions. Use a sufficient number ofwedges to maintain the gap at a suitablesize and to press the boards together, seefigure 103.

In case gluing takes place directly on top ofa concrete slab or a cement mortar screed, itmust be assured that the remaining moistureis less than 65 % RM, when measured inthe temperature interval 17-25°C, seefigure 104. In case there is a need to glue afloor with a higher moisture content in theconcrete, it is required to insert an effectivemoisture barrier, for example bitumen felt,between the subfloor and the wooden floor,see figure 105.

Figure 103 Laying the first parquet blocks with thegrooved edge facing the wall and fixed in place bythe use of distance blocks. It is required to chooseblocks of such length that end joints inneighbouring rows are always staggered minimum80 mm.

Figure 104 Wooden floor, for example parquetblocks glued directly on top of concrete or on ascreed. It must be ensured that the concrete slab isadequately level and dry.

62 GLUED AND NAILED FLOORS

Distance blocks

Minimum 10 mm

Groove

Lim

Concrete

Minimum 80 mm

GrooveTongue

Glue

Concrete

Glue

Woodenfloor

Figure 105 Wooden floor, for example parquetblocks, glued on top of an effective moisturebarrier such as bitumen felt (in case the concreteis too moist gluing the parquet blocks directly ontop). The moisture barrier may be glued to theconcrete slab provided the residual moisturecontent is below 85 % RH.

Figure 106 Wooden floor, for example parquetblocks, glued onto a layer insulating againstimpact sound, which again is glued to the concretesubfloor.

Bitumen felt may be glued to the substrateusing acryl dispersion glue, for exampleparquet glue or glue suitable for gluingPVC-coverings, provided the residualmoisture content is below 85 % RH. Therequirements concerning quality of thebitumen felt to be used are described in thesection regarding Subfloors, bitumen felt(page 13).

In case there is a need for a softer flooror for impact sound reduction it is requiredto insert an intermediate layer, for examplerubber cork. The intermediate layer isglued to the concrete floor, and the woodenfloor is glued to the intermediate layer oncethe glue below the intermediate layer is drysee figure 106.

The underlay must be as uniform and levelas possible in order to ensure the bestpossible adherence. To achieve this it maybe necessary to level the entire floor using alevelling compound.

Porous and very absorbent floors such asconcrete, light weight concrete, anhydrite,gypsum etc. should always be primedbefore gluing. In the case of anhydrite it isrequired to use a special primer, which,apart from securing adherance, alsoprevents the moisture in the glue fromdamaging the substrate.

The flooring materials are glued all overthe surface using a filling glue inaccordance with the recommendationsissued by the floor supplier.

It is advisable to plan the laying of thefloor in such a way that walking on alreadylaid areas is prevented. It is recommendedonly to apply glue to such an area that caneasily be laid withih 15 minutes. The size ofsuch an area will depend on the moistureand temperature conditions in the room aswell as the nature of the material used assubfloor.

It is advisable to load the floor, forexample using sand bags, until the glue hashardened. This is particularly importantalong floor edges.

Walking on newly glued floors should bestrictly avoided until the glue has hardened.The hardening process normally takesminimum 24 hours.

The wooden floor must not be sanded orsurface treated until the parquet blocks arein complete moisture balance with themoisture conditions in the room. This maytake up to 7 days.

GLUED AND NAILED FLOORS 63

Wooden floor

Glue

Glue

Concrete Bitumen felt

Wooden floor

Glue

Concrete GlueImpact sound insulation

The laying of parquet floors using singleblocks.Parquet floors laid as single blocks may belaid in a variety of patterns, for exampleherringbone, Dutch pattern or braidedpattern.Creating patterens is more complicatedthan most other processes in floor laying.Starting a pattern requires meticulous skillsand planning, because the correct laying ofthese first blocks determines the quality ofthe final result, see figures 107-110.Special blocks for the laying on the lefthand side and on the right hand side areavailable for patterned floors. Also specialelements such as squares and narrowbeads in contrasting woods area available.When laying more complicated patterns itis required to cut pieces to size in situ,which again requires excellentcraftsmanship and special tools. Moredetailed information concerning the layingof different patterns may be obtained fromthe parquet floor supplier.

The parquet floor must be sanded afterthe laying, see figure 11. The extent ofsanding required depends on the quality ofthe blocks and should be discussed withthe supplier when choosing type of floor..

Figure 108 Apply glue corresponding to the widthof one row of blocks at a time. Set the blocks inthe glue as close to a neighbouring block aspossible and press the block against neighbouringblocks avoiding glue from being pressed up in thejoint betwqeen the blocks.

Figure 107 The laying of single blocks inherringbone pattern. Set out the centre line of theroom and offset a working line to the right at adistance corresponding to 1/3 of the width of ablock. Set out steering lines perpendicular to theworking line using a big try square. Using a plywoodtemplate will make it easier to place the blocksperpendicular to each other

Figure 109 Laying the last blocks alongthe wall.

64 GLUED AND NAILED FLOORS

Glue

Plywoodtemplate

RulerSetting out lineSetting out line

Glue

Working line

Centre line(of room)

Figure 1 1 0 Place sand bags on the blocks inorder to establish sufficient pressure until theglue has hardened particularly along edges.

Laying mosaic parquet or parquet panels.Mosaic parquet floors are most attractivewhen the pattern is placed symmetrically onthe floor. It is therefore required to measurethe floor before laying in order to determinethe number of full panes in eitherdirection. The remaining space is dividedinto 2 equal parts and indicates thedimension of the adjusted panels along thewalls. In case the size of the adjusted panelsturns out to be less than half a panel it isrequired to add half a panel in order tomaintain the pattern see figures 112-114.

The below mentioned procedure may befollowed when laying the floor: Theposition of the corner of the first panel (inthe center of the floor) is determined. Fromthis point set out (and fix) twostraightedges perpendicular to each otherand parallel to the walls. The first panel isplaced and subsequently a row of panels isplaced along each straightedge The lastpanel in each row is adjusted to size andfixed. The panels are turned in such a waythat the direction of the fibres changes frompanel to panel. The panels are knockedlightly together using a hammering block,carefully avoiding the displacement ofalready laid panels. Laying the remainingpanels takes place diagonally across thefloor.

Figure 1 1 1 The wooden floor is sanded andsurface treated once the glue is completelyhardened and once the floor is in complete moisturebalance with the surrounding environment.

Figure 112 Only apply glue to an areacorresponding to the number of panels that canbe laid within 15 minutes. Start laying the panelsin the center of the room, alteranting between thethe four fields and moving towards the walls.

GLUED AND NAILED FLOORS 65

Lim

Figure 11 3 Laying parquet panels and mosaicparquet. Mosaic parquet where the blocks are buttglued (glued edge to edge) should be broken alongjoints passing through the panel (before laying) insuch a way that the four squares are only joined bythe fabric/mesh on the back side. Set out twoperpendicular centre lines in the room and lay out anumber of panels starting from the centre of theroom and moving towards the walls. Adjust the lastpanel at the wall.

Doors with a thresholdThe floor extends under the threshold. It isrequired to establish a distance of minimum20-30 mm between the parquet blockswhere they meet in the door opening depending on the sizes of the adjoiningfloors. In case the blocks are perpendicularto the door opening, as shown in figure 115,the joints between the blocks should bealigned on the two sides of the threshold.

Figure 114 Place sand bags on the panels in orderto establish sufficient pressure until the glue hashardened particularly along edges.

Figure 11 5 Glued floor with blocksperpendicular to door opening doors with athreshold.

66 GLUED AND NAILED FLOORS

Centre line

Centre line

Big try square

Wooden floor

Glue Concrete

Adjustmentalong the wall

The levels of the floors in adjoing roomsshould be the same. In case this is notpossible, the threshold should be packed tothe level of the highest floor, see figure116.

Doors without a threesholdIt is usual practice to establish a jointbetween the two floors where they meet inthe door opening in order to allow formovements caused by humidity changes.

The joint can be concealed by the use of aflat or curved metal cover strip fixed in oneof the floors only, see figure 117. Thecover strip must not be countersunk intothe floor as this may prevent the freemovement of the floor.

Where there is no threshold, the flooringmay continue through the door openingbetween two smaller rooms. However, it isrequired to dimension the joint along thewalls in both rooms as if the floor were onefloor with a total width corresponding to thewidth of both rooms measured through thedoor opening.

Pipe penetrationsAll holes for pipes shall have a diameter 20mm larger than the pipe going through thehole in order to allow for movements.

Around existing pipes it is possible to cutout a V-shaped block shown in figure 95.After placement of the board, the block isglued back into place and covered with apipe escutcheon.

Figure 1 1 7 It is usual practice to establish ajoint between floors in adjoining rooms, inparticular when the floors are perpendicular toeach other or when they are parallel to the dooropening.

GLUED AND NAILED FLOORS 67

Wooden floor /

Concrete

Figure 1 1 6 Packing the threshold between floatingfloors at different levels.

Wooden floor

Concrete

Packing

Glue

Wooden floor

Figure 11 8 Cutting out for pipes in glued floors.

Glue

Cover strip

Glue

Laying of end grain wood blocks - gluingIdeally, end grain wood blocks should beplaced on top of a wood panel subfloor witha thickness corresponding to the thickness ofthe end blocks. The blocks are laid withjoints running along the long side, seefigures 119-121. Cross joints should be bondlaid, see figures 119-120. A distance ofminimum 20 mm must be observed alongwalls, pipes etc. In order to allow for freefloor movement and expansion, see figures121-122. The best result is normallyachieved by placing thoroughgoing jointsparallel to the shortest walls of the room.

Before laying the floor, it is advisble toconsult the floor supplier concerning choiceof glue tye.

The blocks are glued throughout thesurface, see figures 121-122. They areplaced side by side in the glue and must notbe pushed together as such movement maycause the glue to be pressed up into thejoints, and this may consequently lead tocracks in the joints (or worse in the blockitself) caused by moisture movements in thefloor since the individual movement of theeach block is being restricted.

Laying end grain wood blocks on concreteSome suppliers of end grain wood blocks donot recommend glue fixing due to the risk ofadherence failure caused by lack of concrete

Figure 1 1 9 Place the blocks correctly and inbond sapwood against sapwood heartwoodagainst heartwood.

priming (which is an exacting procedure). .The concrete must be dry before laying witha relative moisture content less the 65%.This requirement also applies to screeds andfiller compounds which must also possesssufficient strength.

Figure 120 Laying end grain wood blocks. Set out centre line of the room and a number of steering linesperpendicular to the centre line. Start laying blocks (in bond) from the centre line towards the walls.

68 GLUED AND NAILED FLOORS

Centre line

Try squareSteering line

Wood panel subfloor

When applying porous self levellingcompounds, for example anhydrite, it isimportant that the concrete surface is cleanof cement slurry and thoroughly primed.

Whenever there is a risk of capillarymoisture rise, it is required to lay out amoisture barrier. When using liquidmoisture barriers such as epoxy basedbarriers it is important to observe therecommended thickness in order to ensurean effective barrier function.

Before laying it is recommended toconsult the floor supplier concerning choiceof primer, moisture barrier and glue type.

Concrete and screeds should be primedand a levelling compound should beapplied, for example a self levellingcompound in order to establish a planesurface without voids or irregularities (+/- 2mm when compared to a 2 m straightedge).Once the floor is dry the surface is sandedwith disk floor sander until the surface isclean and free of burrs and slurry.Subsequently the surface is primed, forexample using parquet glue (diluted to 1:2strength). Once the primer is dry, theblocks are laid as described above

Surface treatmentSanding of the surface may be carried outminimum two days after lying. Sanding dustis completely removed and the floor istreated, for example with floor oil,according to manufacturer s instructions.

The laying end grain wood blocks in sand.End grain wood blocks may also be laid inlayer of sand - 20-30 mm in thickness andlevelled out. Joints are filled with sand.When applying this method, the risk ofblock displacement caused by mechanicalaction and moisture movements is biggercompared to the glued floor. However, it iseasier to make changes and repairs in thistype of floor and the blocks may be reused.The blocks should have a thickness ofminimum 80 mm.

A distance requirement of minimum 20mm should be observed along walls andpipes etc.

The quality of the sand to be used isdescribed in the section Sand, see page 16.

The floor should only be cleaned bysweeping.

GLUED AND NAILED FLOORS 69

End grain wood blocks

Moisture barrier

GlueWood panel

Blocks

Glue

Wood panel

Intermediate layerFigure 121 The blocks are placed in the glue closeto neighbouring blocks and pressed into the glueavoiding glue from being pressed upwards into thejoints.

(Moisture barrier)

Intermediate layer

Figure 122 Cutting out for pipes in end grain woodblock floor.

RENOVATION

When renovating a floor, similarrequirements as those applying to newfloors are to be observed. The floor musthave sufficient strength and stiffness and itmust be firm, dry and plane in order toprovide satisfactory conditions. Old floorcoverings, such as linoleum and carpetsshould be removed which is alsopreferable from indoor climate andhygienic points of view. In case an existingwooden floor is to serve as a subfloor for anew floor, it may be required to re-nail thefloor in order to ensure firmness.

In case it is required to lay floorboards ontop of existing substrates it may be necessaryto level out such substrates in order to meetagreed requirements concerning planenessand levelness. It is normally required thatfloors are level and that deviations fromplaneness fall within ± 2 mm whencompared to a 2m straightedge and ± 0,6mm when compared to 250 mmstraightedge. When carrying out renovationwork it may be very difficult and costly tomeet one or both of these requirements as aresult of building settlement or deformationsor sagging joist. It is therefore required toagree on the accepted tolerances concerningplaneness and levelness before renovationwork takes place.

Levelling may be carried out usinglevelling compounds or, in the case offloorboards, by applying a layer ofmasonite or particle board.

When levelling existing floor joists it isrequired to apply minimum 45 mm thickboards on top of or along the sides ofexisting joists, thereby establishing sufficientsubstrate for nails or screws, see figure 126.

New floorboards nailed on top of oldfloorboards should be laid in the samedirection as the old ones. Nailing shouldtake place only in joists or floor batten andnot in the old boards only.

Floating wooden floors may be laid acrossexisting existing floorboards, see figures123-125. Very thin wooden floors

Figure 124 Laying a new wooden floor with animpact sound insulating layer on top of existingfloor. The threshold may be lifted up by pugging.

(10-14 mm) may in some cases causeuneven elasticity of the floor. This is causedby the fact that the carrying capacity of thesubfloor may vary in different parts of thefloor and also that the joints between thethin boards provide limited stiffness acrossthe floor.

Concrete subfloors must be dry. Incase the pore moisture content exceedsapproximately 65 % in old groundsupported floors or concrete crawl spacedecks or basement floors it should beinvestigated whether moisture is rising frombelow, for example capillary rise of groundmoisture caused by the lack of a moisturebarrier.

70 RENOVATION

New wooden floor

Intermediate layer

Existingconstruction

Figure 123 The laying of a new floor on top ofexisting old floor.

Impact soundinsulation

New floor

Existingconstruction

The laying of diffusion tight or moisturesensitive materials in constructions wheremoisture may rise from below may result indamages, for example adherence failure ordeformation of the wooden floor materials.Before laying a new wooden floor it isimportant to secure the construction with amoisture barrier as described in the sectionmoisture protection - requirements, seepages 26-29.

Figure 126 Straightening existing joists by tackingnew members on the side(s) of the joists. Bytacking members on either side of the joist it ispossible to reduce the distance between supports.

SandingOld wooden floors are often renovated bysanding and thus removing a scruffy anddiscoloured floor surface, for example oldfloor varnish. See also WOOD 47, woodenfloors 2.

Initial sanding is carried out diagonallyusing course sandpaper. Once the floorappears level it is sanded with finersandpaper along the boards. Vacuumcleaning is important between each sanding.The final sanding is carried out using finesandpaper.

In corners, along skirting boards andunder radiators where access with the floorsanding machine is impossible, it isrequired to use a special floor edge sanderwith a rotating round sanding disc. Placesinaccessible to the edge sander are cleanedwith a wood scraper and sanded with a deltasander.

Before sanding old floors with a thicklayer of varnish it is advisable to apply athin layer of special sanding oil in order toprevent the varnish from sticking to thesandpaper during sanding.

JointsRenovating old wooden floors by caulkingexisting joints with a caulking compoundrequires careful assessment and planning. Itis necessary to thoroughly clean the jointand this is best done using a plunge router.In case the floor is oil or lye treated it isrecommended to carry out a test joint beforecaulking the entire floor. The caulked jointis assessed with regards to adherence andcompatibility, typically after curing for 8days. It is recommended to consult caulkingcompound supplier concerning theapplicability of the chosen solution.

Damages in caulked jointsDamages in caulked floor joints may becaused by adherence failure as aconsequence of non compatibility ofcaulking compound and wood specie orcaused by movements larger than the caulkedjoint is able to accept. Such joints must bereplaced by cutting out, cleaning, primingand re-caulking. Notice that renovatedjoints may not achieve the same appearanceas new joints. When replacing caulkingcompound it may be required to re-sand thefloor.

RENOVATION 71

Hard woodcladding

New wooden floor

Impactsoundinsulation

Existingconstruction

Figure 125 Laying a new wooden floor on topof existing floor using impact soundinsulation. The threshold is clad with hardwood

New members tacked onside of joists

Existingconstruction

DAMAGES ANDREPAIRS

Partial repairsLimited damages, for example in a singlefloorboard or in a single parquet block maybe repaired using partial repair orsubstitution.

Floorboards on floor battens or joistsBoards laying on joists or on floor battensare ripped twice along the board and crosscut in two places all cuts are placed 20 mmfrom the edges. A hand held circular sawwith adjustable cutting depth is used. Thedepth is set according to the board thickness.After cutting, the centre piece may beremoved, but it may be required to use achisel in order to cut it loose because of thecircular cut at the ends. Hereafter all theremaining parts of the board may beremoved - using the chisel, and possible glueremains are removed from tongue andgroove of the neighbouring boards. A newboard of the same material is cut to size andthe lower lip of the groove is removed. A 12x 80 mm plywood gusset plate (or similar) isglued to the underside of the remainingboard, serving as support for the new board.The gusset plate is clamped against theboard until the glue has hardened.Subsequently, glue is applied to the gussetplate and to the tongue and groove of theboards, whereafter the board is tilted intoposition, see figure 127.

When boards have T&G on all four sides,it is required to cut off the tongue in the endof the board. When using unsupported buttjoints it is required to support both ends ofthe board using the above describedplywood glued to the underside of theneighbouring boards. It is required to addload to the board until the glue hashardened. Hereafter the board is sandeduntil it becomes level with the neighbouringboards. When single parquet blocks aredamaged it is possible to remove the centrepart by use of a plunge router. Moulding iscarried out minimum 8 mm away fromblock edges. The remaining part of theblock may be removed using a chisel.

Figure 127 Replacing a damaged floorboard placedon floor batten or joists. A plywood gusset plate isinserted between battens/joists and the new board isglue fixed to the plate.

Glued floorsGlued floors consisting of blocks withoutT&G may be repaired using a new blockwhich may be laid and glued directly.

In case the blocks have T&G it isrequired to remove the tongue at one end ofthe block and the lower lip of the groove.The block is placed by inserting the tongueinto the groove along the neighbouringblock, see figure 128. The glue joint must beloaded until the glue has hardened. Hereafterthe block is sanded until it becomes levelwith the neighbouring blocks.

In the case of wood veneer floorboards itis possible to obtain repair blocks allowingfor substitution of single blocks in thetopmost layer, but in most cases it ispreferable to substitute the entire board.

Figure 128 Substituting a damaged parquet blockglued to the substrate. Load must be applied on theblock until the glue has hardened.

72 DAMAGES

Floorboard where the lowerlip of the groove has beenremoved

GluePly wood gusset plate

GlueParquet blockwhere the lower lipof the groove hasbeen removed

SqueakingMost problems related to squeaking floorsare caused by use of wood (for joists andfloor batten) which was not sufficiently drywhen the floor was laid. It is thereforepossible to a large extent to solve mostsuch problems, simply by using dryconstruction timber. Squeaking may occurwhen the wood dries out and shrinks, andthereby creates a cavity between batten/joistand a floorboard. The squeaky sound iscreated when the floorboards, as aconsequence of traffic, are moving up anddown - grinding against the nails.

The squeaking may be removed bypressing the boards against the batten/joistand thereafter re-nailing or screw fixingthem. As a first measure it may be sufficientto hammer the existing nails deeper into theconstruction by placing a large woodenblock on top of the floor and hammer on inwith a big hammer.

Squeaking may also be caused by the factthat the floor has been nailed with a nailinggun, using secret nailing and for examplewire nails. If the floorboards have not beenpressed sufficiently tight against thebatten/joist, the boards will rest on the wirenails. This will cause squeaking betweenboard and batten/joist, because the boardsare not properly fixed.

Squeaking also occurs when wood veneerfloorboards, with a core made of particleboard, are fixed using secret nailing, becausethe nails do not get a proper grip in the softcore. In this case the only way to removesqueaking is re-nailing from the topside.

When re-nailing old floorboards fromabove it is recommended to use ringed andtwisted flooring nails, for example 3.5 x55 mm for boards 20-22 mm in thickness,and 3.8 x 65 mm for boards 25-28 mm inthickness. Re-nailing should only be carriedout at such a time when it is absolutelycertain that the battens/joists are in moistureequilibrium with the surrounding air. Whenre-nailing a floor where secret nailing hasbeen used in the first place, it is most oftenpossible to detect the placement ofbattens/joists by knocking on the floor or bythe use of a metal detector.

Squeaking may also be caused by failure inthe subfloor, either caused by thedisplacement of some of the packing pieces,or because the battens/joists have not beenproperly levelled out. After some time asmall space may occur between the boardsand the battens/joist which have sagged.This causes movement of the boards inrelation to the nails and squeaking occursand the floor seems to give way.

So far no safe methods may be prescribedin order to repair failure in battens/joists.In some cases an acceptable solution maybe achieved by pulling the batten and theboard together using screws from above.

Special screws, with a course self tappingthread, have been developed with thespecific purpose of repairing battenconstructions where the packing has failed.The screw is driven through the battenwhereby it cuts a thread. By adjusting thescrew it is possible to lift or to lower thebatten and thereby substituting the packinglocally, see figure 129.

When using special screws, care must betaken not to damage pipes and cables whichmay run under the floor. B

In case of extensive damages, the onlyrepair method recommended is re-laying theentire floor.

Figure 129 Floor-Jack screw may be used in casethe packing fails locally. Do not tighten the screwexcessively as this may cause the lifting of the floor.

DAMAGES 73

Wooden floor - Wooden plug

Floor batten

-Floor-Jack screw

Figure 130 Cupping of boards wash board most often caused by moisture on the underside ofthe boards. .

Curved boardsIn case the floor is laid on a moist substratethe backside will absorb the moisture andexpand. This may cause lasting deformationsin the form of curved boards, often referredto as wash board, see figure 130. Washboard may be prevented by ensuring a drysubstrate or by the use of a moisture barrier.In case the deformation is caused byconstruction moisture it may be possible toalleviate the problem by sanding the floor,once the building has reached moistureequilibrium.

In case the problem is caused by risingground moisture it is most likelynecessary to insert a moisture barrier. In thiscase it is required to re-lay the floor.

Wash board may also occur when layingfloorboards with a moisture content of 12-17 %. When the floor dries out to 6-8 %moisture content, the boards will dry out onthe top side first, thereby causing them tocurve.

Pressure shrinkage and expansionpressureIn case a wooden floor is moisturized afterlaying, it may expand considerably and thismay cause problems. In case the boards arebeing prevented from moving, for examplewhen they meet a column or a wall, the cellsin the wood will be pressed together, and theboards will appear visibly narrower afterdrying out again. This phenomenon is knownas pressure shrinkage.

In case the forces become excessive thefloor will either bulge, which normallyhappens to floating floors, or in severecases, it may push out the walls.

When a wooden pine floor with 10 %moisture content just touches thesurrounding walls, the pressure it mayexercise when moisturized during use mayreach approximately 2.5 N/mm2 radially andapproximately 1.5 N/mm2 tangentially.Assuming an average of 2 N/mm2, a 22 mmboard may exercise a pressure correspondingto 2 x 22 x 1000 N/lnm, equallingapproximately 4.4 tonnes per meter!!!

Repairing damages caused by moistureexpansion is done by cutting along suchedges that are prevented from freemovement. The aesthetic damages, in termsof cracks, are difficult to repair with a goodresult. In case of minor damages it may besufficient to re-sand the floor; otherwise itmay be necessary to re-lay the entire floor.

CracksWhen drying out the floor will shrink andnatural joints will occur between the boardsor blocks. In cases where the moisturedetermined shrinkage is hindered, it maycause excessive partial cracks, because thetensions which are built up in the wood willbe released in the weakest ponts. In manycases the shrinkage will be concentrated insingle joints or in single boards. The cracksoccurring in such instances will have awidth corresponding to the total shrinkageof the floor. This is a widely knownproblem in floating floors which, in manycases, are being fixed in position by heavyloads from furniture and equipment orcolumns and hard and strongly adhesivecaulking compounds in joints (which inmany cases are carried out without the useof backstopping at the bottom of the joint).

Alleviating such problems may be done byinserting a dilatation joint in the crack. Incase the dilatation joints are planned beforethe floor is laid, it is possible to control inwhich areas the floor must be able to movefreely, and also how wide the dilatationjoints should be.

74 DAMAGES

APPENDIX

Moisture measuringIn order to assess moisture conditions, forexample construction moisture, beforelaying a wooden floor or in order todetermine causes of damage, it is necessaryto be able to measure moisture. Moisturemeasuring in relation to wooden floorsincludes measuring of relative air humidity,measuring moisture in subfloors,particularly in concrete in light weightconcrete and measuring of moisture in woodmaterials. Below, a number of thecommonly used methods are describedbriefly. A more extensive description ofthe methods may be found in SBI-Directive 170: Measuring methods used inbuilding analyses; GSO Floorfacts (Gulvfakta) and various standards.When measuring moisture, special attentionshould be given to the following aspects:

The user must be confident with theequipment used and must be able toassess the results.Apart from the ability to use ordinarymoisture check methods, it is also aprecondition that the user possessesknowledge about building physics in orderto be able to assess the results.Moisture conditions in a constructionmay vary considerably from one area toanother. Consequently, it may benecessary to carry out several tests inorder to get a correct image of theconditions.The tests should be carried out over asufficiently long period in order to makesure that moisture conditions are inequilibrium.Moisture conditions may varyconsiderably throughout the year, andassessment of results must consider thisfact.

Measuring moisture variations insubstrates capacitive moisture meterThe measuring instrument, which is cheapand easy to use, is placed directly on top ofthe surface of the material to be tested, seefigure 131. When measuring, the result isshown as a value depending on the moisturecontent.

Figure 131 Moisture meter Capacitive moisturemeter suitable for detecting differences inmoisture content.

Capacitive moisture meters are not suitablefor the testing of absolute moisture contentexpressed in %. However, they are wellsuited for finding differences in moisturecontent, for example for the spotting out ofparticularly dry or particularly wet areas ofa floor. The meter is non-destructive as itmeasures on the surface with a measuringdept of up to 35 mm.

The Appendix: Moisture measuring inconcrete gives a more comprehensiveexplanation of the steps to be followedwhen detecting wet and dry areas ofconcrete subfloors. Reference is also madeto GSO Floor fact (Gulvfakta).

Measuring of moisture in concrete andlight weight concrete relative moisture ina drilled test hole.The most commonly applied method formeasuring moisture in concrete is tomeasure the air humidity in a drilled hole inthe concrete. Normally, a hole with adepth corresponding to 0.4 x the thicknessof the concrete slab is drilled. After vacuumcleaning the hole, a probe is inserted intothe hole and the hole is sealed off in orderto allow the establishment equilibriumbetween probe and the relative air humidityin the hole. It normally takes from severalhours up to several days until equilibrium isachieved, see figures 132 and 136.

MEASURING MOISTURE 75

Figure 132 Electronic moisture meter for themeasuring of relative air humidity and relative airhumidity in a drilled hole in concrete or in lightweight concrete.

As an alternative it is possible to take outsamples which are subsequently placed inplastic containers with a tight fitting lid, andthe testing is carried out inside thecontainer. The taking out of samples mustbe done manually, for example bychiselling, as water or heating from a water-cooled drilling machine may distort the testmaterial.

Measuring relative moisture contentusing a psychrometer.When using a psychrometer it is possible tomake an instant measuring of moisturecontent. A psychrometer consists of twoprecision thermometers of which one iscovered with moistened muslin wick. Theair passes by both thermometers andevaporation takes place around themoistened muslin wick causing cooling.The difference in temperature between the

wet and the dry thermometer is anexpression of the relative air humidity. Themethod is relatively accurate and is oftenused for calibrating other meter types, forexample the thermo hygrograph.

Measuring temperature and relativeair humidity using a thermohygrograph.A thermo-hygrograph consists of a bimetalthermometer and a hygrometer shaped as ahair harp. Both parts are connected to a penwhich records the measured values on arotating drum supplied with a sheet ofrecording paper. The drum makes one fullturn over a certain period of time normally one week. The result is acomplete record of temperature andmoisture variance during the period.

As is the case with all types ofhygrometers, it is required to regenerate andcalibrate the hair harp at relatively shortintervals in order to get reliable results, cf.SBI-Direction 170.

Measuring temperature and relativeair moisture using a data-loggerData-loggers are comparatively newdevices used for the measuring oftemperature and relative air humidity, seefigure 133. They are operated via a PC and

76 MEASURING MOISTURE

Figure 133 Data logger for the measuring oftemperature and relative air humidity.

may be programmed for measuring duringvarying time intervals, from a few minutesup to several months. Measuring and datacollection take place by means of a smallelectronic device, and does not requirelinking up with cables during measuring.After measuring, all data are transferred toa PC for further processing.

Testing moisture content in wood using anelectric resistance meter (pin type meter)The most commonly used instrument formoisture measuring in wood on thebuilding site is a moisture meter based onthe measuring of electric resistancebetween two electrodes knocked orpierced into the wood, see figure 134. Themethod is based on the fact that the electricresistance between the electrodes dependson the moisture content in the wood. Themarket offers a variety of brands, but inprinciple only two different types. Onetype is supplied with insulated electrodes,which only allows for measuring at the tipof the electrode. This may be an advantagesince the method prevents disturbances inthe test result, for example caused bycondensed water on the surface. The othertype is supplied without this insulation andis often cheaper and easier to work with.

Measuring takes place along the grainsand never across cracks or knots or close tonails or screws. It is required to measure ata distance of minimum 300 mm from endwood and as a minimum measuring shouldtake place in three different places, seefigure 135.

The moisture content in floorboardsshould be measured at both ends of theboard as the density at top end and root endvaries. As a result the moisture content andthe drying out time differ in the two ends.

Most instruments indicate the moisturecontent directly in %. The instruments arenormally calibrated for the measuring ofpine and spruce and it is required to adjusttest results when measuring in othermaterials and species. Likewise, it isrequired to adjust results when thetemperature deviates considerably from20°C.

Liquids used for pressure impregnationmay change the conductivity of the woodcausing results to be unreliable in pressureimpregnated wood.

Figure 134 Electric resistance meter for themeasuring of moisture content in wood.

Figure 135 Measuring takes place along the grainsand at a distance of minimum 300 mm from ends.

MEASURING MOISTURE 77

Measuring moisture in concreteBefore laying wooden floors on concrete orlight weight concrete substrates it is requiredto ensure that the moisture content in thesubfloor does not harm the wooden floormaterials. The procedure used when testingmoisture content in concrete is brieflydescribed below. A more thorough descriptionof methods may be found in GSO Floorfacts (Gulv-fakta).

ProcedureThe floor is subdivided by means of amodular grid in such a way that each fieldcovers approximately 10 m2. Initial testing iscarried out using non-destructive testingequipment, for example a capacitive moisturemeter at every modular grid intersectionpoint, in order to determine most wet andmost dry areas. Subsequent measuring is

carried out using equipment for the measuringof relative moisture in a number of drilledholes, see figure 136.

Measuring is carried out in most wet andin most dry areas as well as in normalareas. Normal areas are defined as suchareas having a moisture content averagingthe two extremes. The number of testsdepends on floor size, see table 6

Table 6 Number of moisture test per floor

Floorsize inm2

Number of non-destructivetests

Number ofrelative moisturecontent tests

up to100 14 2up to200 27 4up to 400 54 5up to 600 80 6above 600 14 per. m2 1 per 100 m2

Notice that the measuring of relative moisturecontent inside in a drilled hole should takeplace over considerable time in order toestablish equilibrium between moisture in theconcrete and the relative air moisture insidethe hole, see Appendix: Moisture measuring,page 75, concerning the testing of moisturein concrete and in light weight concrete.

Figure 136 Measuring moisture in concrete bymeasuring the relative air moisture inside drilledholes. Notice that the moisture content in theconcrete substrate is levelled out by the applicationof a diffusion tight cover, for example bitumen felt.At the bottom of the hole (approximately 0.4 xconcrete thickness) the moisture content is more orless unchanged.

In case wooden floors are laid directlyon top of concrete it is required that themoisture content in the concrete is lessthan 65 % relative moisture content.

When bitumen felt is used a moisturebarrier below the wooden floor, themoisture content in the concrete shall beless than 85 % relative moisture content inorder to allow for the glue to harden.

78 MEASURING MOISTURE

Moisture meter

Drilled hole

0.4xconcretethickness (B)

Tight covering

Drilled hole Drilled hole-

% RM%RM

Seal

Acceptance checkWhen wooden materials are received at abuilding site it is recommended to carry outan acceptance check including such aspectsas visible mechanical defects, number ofpieces, dimensions, wood quality etc

In the case of wooden materials such asboards and floor battens it is alsorecommended to assess wood moisturecontent as this is a hidden quality. Standardsshould be defined for moisture content, forexample 12 % average moisture content,which is a realistic demand in the example offloor battens. In case the wood moisturecontent does not correspond to the setstandard, problems may arise later.

The moisture content is controlled bytaking out samples. It is advisable todetermine how samples should be takenbeforehand, i.e. how many samples shouldbe taken, how they are measured and howtest results are handled/assessed.

The number of samples included in theacceptance check depends on the totalnumber of boards, battens or blocksincluded in the acceptance check and thechosen quality class.

Table 7 lists up some proposalsconcerning the number of samplesnecessary in connection with minor jobs

Table 7 Proposed number of samples to betaken in connection with minor jobs.Numberm2 in job

Number ofsamples

Kiln driedboards/blocks

Air dried items

2-89-15

23

23

16-2526-50

45

45

51-9091-150

81

913

151-280281-500

1827

2032

501-999above 1000

364

4560

EDG-Recommendation issued 22nd

October 1994 specifies three moistureclasses for wood and wood based material:Standard (S), Quality (Q) and Exclusive(E). Each class defines tolerances as to theaccepted deviations from desired moisturecontent (measured value). For classStandard the accepted deviations are ± 0.3 xmeasured value, and for Quality theaccepted deviations are ± 0.2 x measuredvalue.

As for kiln dried boards it may bedesirable to accept a symmetrical intervalaround the desired value, like for example8% ± 2 %, With respect to floor battensand joist, normally only the upper values areof interest. Thus, the requirement maydefine that a maximum of 5 % of measuredvalues exceed a defined upper limit. Forsamples with a very limited number ofresults one may, as an alternative, definerequirements such as: number of samples,maximum average moisture content, utarg,and number of results accepted to exceed utargwith + 2 or +3 %.

In connection with larger jobs it is importantto be able to get a clear picture of the testresults, the deviations and the unequaldistribution of values which is bound toexist in a batch of kiln dried wood.

This applies particularly to wood materialsfrom a sawmill whereas such materials likeparquets blocks and panelled wood oftenhave a very constant average moisturecontent with very little deviation from theaverage figure.

ACCEPTANCE CHECK 79

Example 1:Ten samples with an average moisture content of12 % are required. Further, only one out of tenresults is accepted to equal or be higher than 14 %.In case one result is higher than or equals 14 %, itis required to make ten new tests and none ofthese results must be higher than or equal 14 %.

Concluding: the ten results must have an averagemoisture content of 12 % and at the same time fulfilthe requirement of being less than 14 %.

The starting point is class Standard, andthe requirement is that 95 % of results fallbelow 12 + 0.3 x 12 i.e. below 15.6 %,considering that the requirement isunilateral (requirement to maximummoisture content only). It is evident thatthis requirement is fulfilled as only one testresult, corresponding to 2 % falls outsidethe interval.

In case the requirement is Quality it isrequired that 95 % of results fall below 12+ 0.2 x 12, i.e. below 14.4 %. Four testresults, corresponding to 8 %, fall above theupper limit. Considering this qualityrequirement, it is obvious that the batchmust be rejected.

PlanenessThe testing of levelness of substrates andfloors is briefly mentioned here. For moredetailed information, reference is made toGSO Floor facts (Gulvfakta).

Notice, it is very important to agree uponwhat requirements shall be fulfilled, andhow to test fulfilment of requirements. Incase reference is made to different testmethods, it will not be possible to compareresults.

The general requirement to floors is thatthey must be plane and level. Planeness isdefined in such a way that all points of thefloor fall within the same plane which maybe level or may be sloping. Deviationsmay show as cavities or as elevations. Alevel floor is a floor where all points fallwithin the same plane and the plane is levelat the same time. Deviations from this aredefined as floor slope.

Normally, planeness falls within ± 2 mmwhen compared to a 2 m straightedge (and± 0.6 mm when compared to a 250 mmstraightedge), see figure 137.

Planeness requirements are not onlyapplicable to the floor surface but also tothe substrate, i.e. the upper side of floorbattens in the case of suspended floors andthe substrate itself for other floor types.

Table 8 Registering moisture test result. Noticeasymmetric moisture graph.Woodmoisturecontent

% Number Accumulatednumber%

789

10IIIIIIIIIIIIIII

510

515

1030

1112

IIIIIIIIIIIIIIIIIIIII

129

2736

5472

1314

IIIIIIIIII

64

4246

8492

1516

IIII

31

4950

98100

1718

Figure 137 Testing planeness by the use ofstraightedges 250 mm and 2000 mmrespectively.

80 ACCEPTANCE CHECK

Example 2:A batch consisting of 500 pine planks, 50 x100 mm (for floor battens) may have amoisture content of 12 %. The number ofsamples is 50. It has been agreed to use anelectric resistance meter with insulatedelectrodes penetrating 1/3 of the thickness onthe broad side in the centre of the planks only one test per plank.

The individual test results are entered andcomputed as indicated in table 8.

0.25 m0.6 mm

Cavity

Cavity

0.6 mmElevation

Elevation

Testing and testing equipmentTesting tools are straightedges with alength of 2 (2mm high legs) and 0.25 m(0.6 mm high legs).

When controlling planeness, firstcompare floor with the side of straightedgewithout legs. Push straightedge across thefloor in order to detect irregularities. Checkwhole floor area, but pay special attentionto areas along walls and in front of windowsand doors. When irregularities are detected,turn round the straightedge in order to makeit rest on the legs. Irrespective ofplacement, the maximum distance betweenfloor and straightedge must not exceed 4mm and 1.2 mm for 2 m and 0.25 mstraightedges respectively. Further, thestraightedge must rest on both legs otherwise the planeness requirements arenot fulfilled.

The distance between floor andstraightedge is most easily controlled byuse of a testing brick with a thicknesscorresponding to 2 x the tolerance, forexample a 4 mm brick when checkingtolerances of ± 2 mm, and a 1.2 mm brickwhen checking tolerances of ± 0,6 mm.

ElasticityA certain degree of elasticity is accepted inwooden floors. However, the elasticityshould not be excessive as this may result inannoying vibrations, for example shakingfurniture or chinking noise from porcelainin cupboards caused by persons walking onthe floor.

A precondition for the establishment of astable floor is the correct functioning ofsupport systems for floor battens. Thesupports must be strong and it must bepossible to fix the supports properly to thebattens. The taller the support is, the higherare the requirements to stifness/inelasiticityof the same in order to reduce deformationscaused by traffic on the floor. When usingvery tall supports, i.e. supports exceeding100 mm, it is recommended to use inelasticmaterials such as bricks or concrete for thelower part of the support (in stead of moreelastic materials such as plastic). Soft boardbricks are generally carried out indimensions as indicated on page 13.

Floors on floor battens: Whendimensioned in accordance with tables 4and 5, a deflection of maximum 2 mm(caused by walking) is accepted. Thedeflection is either measured along thecentreline between two battens, or on abatten halfway between two supports, seefigure 138.

between battens or between supports >

Figure 138 The accepted tolerance for deflection ona floor on battens is 2 mm between battens andbetween supports.

PLANENESS 81

Maximum deflection 2 mm

WOODEN FLOORS AND BRREQUIREMENTSThe Building Regulations 1995 define thefollowing requirements to wooden floors:

Escape routesFloor coverings in escape routes, assemblyrooms and in shops with a floor areaexceeding 150 m2 shall be suitably fireresistant class Dfl s1 (class G floorcoverings). This requirement may be metwhen using for example 21 mm tongued andgrooved floor or a wooden flooring withpermanent fireproof bonding to non-combustible base.The use of wooden coverings with athickness of less than 21 mm and without apermanent fireproof bonding to non-combustible base shall be tested inaccordance with d NT 007/DS 1063.2. Alsosee Wood 38 Wood and Fire (Træ 38, Træ ogbrand).

FireplacesThe floor shall be constructed of a non-combustible material or covered with anon-combustible cladding extending 300mm in front of closed fireplaces and 500mm in front of open fireplaces. Also thematerial must extent minimum 150 mm toeither side of the fireplace opening.

ChimneysWooden floor coverings with a thicknessexceeding 30 mm may be brought into closecontact with outer side of a brick chimneywall (minimum 228 mm wall or similar, forexample a lining). In the case of steelchimneys, a distance of 50 mm between fluepipe and boards must be observed.

Moisture insulationOnly general remarks - reference is made toSBI Direction 178 concerning moistureinsulation in buildings.

Sound insulationThe Building Regulations do definerequirements to sound insulation in storeypartitions, and consequently requirementsto impact sound etc.

82 BR REQUIREMENTS

TERMINOLOGY

BoardsCommercial name for converted (sawn)timber with a thickness of minimum 16 mmand minimum 75 mm in width corresponding to minimum 12 x 68 mm forplaned boards.

BurrA fin of concrete, for example from aformwork joint or a fin left when using astraightedge for levelling wet concrete.

CalibrateTesting instruments shall be calibrated inorder to secure that test results are correct.In principle, the calibration is carried outby comparing the instrument in questionwith a more accurate instrument. In mostcases is only a matter of adjusting theinstrument reading to make it correspondwith the reading on the masterinstrument, otherwise it may be necessaryto work out a table or a graph which willindicate how test result can be converted tothe correct values.

CompressionCompression of fibres in a piece of woodcausing permanent deformation.

ContinuousContinuous indicates that a piece of wood ora building component continuesuninterrupted through an openeing , forexample floorboards through a dooropening.

DepressionLocal subsidence of the surface.

Dilatation jointA joint specially designed to absorbmovements in building components andelements, for example in floors.

Unsupported butt jointUnsupported butt joints are are end to endjoints which are not supported, for exampleend to end joints between floorboards.

Dispersion glueType of glue where the siccative is evenlydistributed in the solvent. When used forfloors, the siccative is often based on acrylicresin or PVA and the solvent is water.

Elastic layerA layer inserted in a floating floor betweenthe floor covering and the load carryingsubfloor in order to achieve the desiredflexibility in the floor.

EPDMSpecial type of rubber (Ethylene PropyleneDiene Monomer).

FishplatesA joint between wood members carried outby nailing (or screwing) an additional pieceof wood on either side of the two membersto be joined, see page 46, figure 61.

HDFHigh Density Fibre board is ahomogeneous wood fibre boardcompressed even more than MDF. Thedensity of HDF board is approximately870-1070 kg/m3.

Insulation jointInsulation joints are used to separate floorsfrom adjacent building components such ascolumns and walls in order to preventdamages, for example caused by moistureexpansion.

LevelnessLevelness indicates that a floor is plane andthat the plane is level. Deviations aredetected as floor slope, see figure 141.

TERMINOLOGY 83

Figures 141, Deviations from level are detected as floorslope.

Load distributing board/pressuredistributing layerA layer which in floating floors accept theload and distribute it evenly on a largersurface, for example a particle boarddistributing the load on insulationsubstrate.

Local defect Areas with uneven surface, forexample caused by burrs or cavities. Inwooden floors a local defect may be thelevel difference between neighbouring floorboards or blocks, see figure 139

MDFMedium Density Fibre board is ahomogeneous wood fibre board made ofcompressed/glued fine wood fibres. Thedensity of MDF board is approximately640-720 kg/m3.

OSBOriented Strand Board are boards made ofwood filaments cross bond in order to givethe board greater strength and dimensionstability

Piling sticksWhen stacking boards or planks it isimportant to insert thin sticks between thelayers in order to allow the air to circulatefreely.

Plain sawnAlso referred to as crown sawn orthrough and through is obtained by

sawing tangentially to the annual rings.Often gives a flamy look on board facescaused by the cone-shape of the trunk.

PlanenessPlaneness indicates that all points of thefloor are positioned within the same planewhich may be level or sloping. Deviationsare defined as depressions (cavities) orelevations, see figure 140.

PlanksCommercial name for converted (sawn)timber with a thickness of minimum 50 andminimum 100 mm in width corresponding to minimum 43 x 92 mmstraightened and planed planks. Floorboardsare very often referred to as flooring planks.However, the use of this term is misguidingsince the boards do not have plankdimensions.

PVAPolyVinyl Acetate is commonly used infloor glues.

Quarter sawnBoards are radial cut from the centre of thetree. It produces the distinctive silverribbon effect (in oak) across the wholeboard. Annual growth rings form an anglegreater than 45 degrees. True quarteredboards producing the best features will havethe angle on or very much closer to 90degrees

RadonRadioactive gas existing underground. Sincethe gas emits radiation, it is important toprevent the gas from entering buildings.

RegenerateRegeneration of the hair harp in ahygrometer or in a thermo hygrograph iscarried out in order to maintain the hair schange in length when exposed tomoisture.

Ship plank jointsSpecial joint made with loose fillet orcaulking compound in order to make thefloor look like a ship s deck. The joint isoften carried out in colours contrasting thefloorboards.

°Shore AShore A expresses the hardness of a material(for example elastometric compounds). Thehigher the value is the harder is the material.

Figure 140 Testing planeness. Deviations aredefined as cavities or elevations.

84 TERMINOLOGY

.

StraightedgeA completely straight board or rail used asreference when assessing planeness ofsurfacedefects

ToleranceTolerance defines limits for deviationsaccepted. It is common practice to use asymmetric tolerance, i.e. the deviation maybe positive or negative, for example ± 2mm..

»Wash board«Regular repeated unevenness of the floorsurface where boards are cupping caused byexpansion of the underside of the board, seefigure 142.

WarpingWarping indicates that the four corners ofa board or a block do not lie in the sameplane (typically caused by twisting of thewood).

Packed baseReferring to shocking up systems. Anycombination of packing pieces is referred toas a packed base.

LITERATURE

Danish Building Research Institute (SBI):Testing methods in buildinginvestigations. Erik Brandt, SBI-direction170, 1990.Sound insulation in buildings - newbuildings, J0rgen Kristensen, SBI-direction172, 1992.Sound insulation in buildings - oldbuildings, J0rgen Kristensen, SBI-direction173, 1992.Moisture insulation in buildings, NilsErik Andersen and others. SBI-direction178, 1993.Single Family Houses - design, SBI-direction 189, 1997.Wet rooms, Erik Brandt, By and BygDirection 200, 2001.

The Wood Industry Advisory Council:WOOD 32, Plywood, 1991.WOOD 36, Wood fibre boards, 1993.WOOD 37, Particle board in building

construction, 1994.WOOD 38, Wood and fire, 1995.WOOD 47, Wooden floors 2 the choiceof and maintenance, 2001.WOOD 50, Wood quality andcharacteristics, 2003

Hands on leaflets:Moisture in wooden floors on top ofheavily insulated ground supportedfloors. (13)950224Ground supported floors with woodenfloors on battens and with heating pipes,(13)980924Water damage in wooden floors,

(43)930113Caulked joints in wooden floors,

(43)990923Swelling of wooden floors caused by(construction)moisture, (43)991123

Others:

GSO Floor facts (Gulvfakta)Gulvbranchens Samar-bejds- og Oplysningsrad.FSO Caulking guide, FugebranchensSamarbejds- og Oplysningsrad, 2004.

LITERATURE 85

Wash board - cupping

Figure 142 Wash board caused by cupping

SUBJECT INDEX

Acceptance check, p. 79 Floating floors, p. 4, 39, 54Air gun nails, p. 18 Floor battens - distances, p. 44Aspects related to sound, p. 38 Floor battens, p. 11

Floor battens, p. 11,47Bitumen felt, p. 13 Floor construction, p. 6Boards, p. 83 Floor heating systems, p. 32Burr, p. 83 Floor heating, p. 31

Floor on battens, p. 4, 38, 43Calibrate, p. 83 Floor on joists, p. 4Capacitive moisture meter, p. 75 Floor types, p. 6Caulking compound, p. 41 Floorboards, p. 7Chimneys, p. 82 Flooring cardboard, p. 15Chipboard screws, p. 19 Flooring nails, p. 18Click joints , p. 21 Foam plastic, p. 15Clips, p. 21Compression, p. 85 Glue, p. 20Concrete slab, p. 16 Glued floors, p. 5, 59Continuous, p. 83 Gluing bitumen felt, p. 20Cork dust sheet, p. 15 Gluing entire face, p. 20Cork rubber, p. 15 Gluing T & G , p. 20Cracks, p. 74Cupping boards, p. 74 HDF, p.83Curved boards, p. 51

Impact sound reducing materials, p. 15Data-logger, p. 76 Insulation joint, p. 40, 83Depression, p. 84 Insulation materials, p. 13Dilatation joint, p. 40, 83Dispersion glue, p. 83 Joints, p. 40, 71

Joist distance, p. 44Elastic layer, p. 83 Joist floor, p. 16Elasticity, p. 81Electric resistance meter , p. 77 Laminate floorboards , p. 10End grain wood blocks p. 10 Laying instructions, p. 43EPDM, p. 83 Levelness, p. 85Escape routes, p. 82 Load distributing board, p. 83Expansion pressure, p. 74 Local defect, p. 83

Finishing nails, p. 18 MDF, p. 84Fire places, p. 82 Measuring, p. 81Fish plate, p. 83 Moisture barrier, p. 14

86 SUBJECT INDEX

Moisture barrier, p. 14Moisture insulation, p. 82 Screed, p. 16Moisture measuring in concrete, p. 78 Screws, p. 17, 19Moisture measuring, p. 75 Ships plank joint, p. 42, 84Monta-flex, p. 19 "Shore A , p. 84Mosaic parquet, p. 9, 65 Shrinkage, p. 22Movement profile, p. 42 Soft blocks, p. 13

Sound insulation, p. 82Nailed floors, p. 5, 59 Spacers, p. 24Nails, p. 17, 18 Squeaking floors, p. 18, 73Non-suspended floors, p. 4 Staples, p. 18

Straightedge, p. 84OSB, p. 84 Stress relief groove, p. 46

Support distances, p. 43Packing pieces -distances, p.47 Suspended floors, p. 4Packing pieces, p. 12, 44Partial repairs, p. 72 10-board measurement, p. 24Parquet blocks, p. 8 Testing equipment, p. 81Parquet boards, p. 8 Thermo hygrograph, p. 76Parquet floors, p. 64 T-nails, p. 17Parquet tiles, p. 9, 65 Tolerance, p. 85Piling wood , p. 84Plain sawn, p. 84 Unsupported joint, p. 51,83Planeness, p. 80, 84Planks, p. 84 Veneered boards, p. 10Plastic foils, p. 14Plata-Flex, p. 19 Warp, p. 85Pressure distributing layer, p. 83 Wash board, p. 85Pressure shrinkage, p. 74 Wet rooms, p. 36Psychrometer, p. 76 Wood block floor, p. 68

PVAc, p. 84Wood expansion, p.22Wood veneer floorboards, p.9

Quarter sawn, p. 85

Radon, p. 84Regenerate, p. 84Renovating, p. 70Repairs, p. 72Rubber cork, p. 15

Sand, p. 16Sanding, p. 71

SUBJECT INDEX 87

The book has been elaborated by the Danish BuildingResearch Institute in collaboration and The Wood IndustryAdvisory Council in collaboration with: e

The Confederation of Danish IndustriesCasco Glue A/SDana Glue A/SDitas A/SFaxe A/SFugebranchens Samarbejds- og OplysningsradGS Trapper og GulveGulvbranchens Samarbejds- og OplysningsradH0rning Parket Fabrik A/STimberman Denmark A/SJunckers Industrier A/SKnudsen Kilen A/SKahrs Danmark A/SMoland Byggevarer A/SITW Construction Products ApSRockwool A/SSkandinavisk Timport ApSSunds Paneler/Parket A/STarkett Danmark A/SThermisol A/STool-Matic A/STrip Trap Denmark A/SVibopan v/Novopan Traindustri A/SWoodfloor A/S

Manuscript: Senior researcher civil engineer ErikBrandt,

By and Byg, Danish Building Research InstituteEdited by: The Wood Industry Advisory Council

Graphic planning: Trine PreislerDrawings: Peter Nielsen Concept & illustration

Photography: Per Jacobsen Photography and DigitalStudio

Print: Gøtze Grafisk, Herning

Copyright © 2004: Wood Industry AdvisoryCouncil 3. edition, 1st print,June 2004

Copying only allowed with permission from:The Wood Industry Advisory Council

Lyngby Kirkestreede 14,2800 Kgs. LyngbyPhone 45 28 03 33

Fax 45 28 03 30top@top.dkwww.top.dk

ISBN: 87-90856 59-7

The handbook demonstrates

thoroughly tested methods for

the laying of wooden floors and

describes such technical

conditions which must be

fulfilled in order to constructwooden floors correctly. The

book has been elaborated by The

Danish Building Research

Institute and The Wood Industry

Advisory Council.

Translation into English:

Karsten Lundager,

University College Vitus Bering

Denmark

WOOD INDUSTRY ADVISORYCOUNCIL