TimberThe term "timber" describes sawn wood that is 140mm or more in its smallest dimension. There are two categories of timbers. Rectangular "Beams and Stringers" (width more than 51mm greater than thickness) are typically used as bending members, and square "Posts and Timbers" (width less than 51mm greater than thickness) are typically used for columns.[footnoteRef:1] [1: Canadian Wood Council, Timber - http://cwc.ca/wood-products/lumber/timber/. Retrieved 16.04.2014]

Wood timbers and construction most commonly are related with such a general terms as timber framing and post-and beam constructions. That means building with heavy timbers rather than using dimensional lumber. Method is realized by using heavy squared-off and carefully fitted and joined timbers to create a structures. Generally it can be seen in buildings which are from 19th century and earlier. Usage of timber and timber framing method can be considered as base or principle for modern wood treatment and material manufacturing. The only difference is technology, because comparing development and progress, the way how things were done are different. In those times saws were used to cut lumber from the starting material stock, then with the help of axes, draw knifes and other hand powered tools details/materials were assembled together to make a structure for a building which was capable of bearing weight of itself and other parts. In nowadays materials available from lumber yard stocks are usually made by cutting large timbers in logs, which comes in sizes up to 394 x 394mm. Availability of large size and long length timbers are set by pre-order from suppliers, specifying the request.There has been little in-grade strength test data on timbers, due to the relatively small volume of timbers produced. Therefore, the design values for timbers are determined on the basis of small clear tests adapted for grade characteristics. Generally timbers, along with other materials, for example glulam and laminated veneer lumber (LVL), are used for post and beam constructions.

Sizes/DimensionsTimbers are sometimes manufactured to large dimensions and resawn later to fulfill specific orders. The table below shows the most common sizes, which range from 140mm x 140mm to 292 x 495mm in lengths of 5m to 9m and longer, with longer lengths which means a bigger price.Table 1: Timber Sizes[footnoteRef:2] [2: Canadian Wood Council, Timber - http://cwc.ca/wood-products/lumber/timber/, Retrieved 16.04.2014]

140 x 140Post and Timber

x191

x241

Beam and Stringer

x292

x343

x394

x445

191 x 191Post and Timber

x241

x292

Beam and Stringer

x343

x394

x445

x495

241 x 241Post and Timber

x292

x343Beam and Stringer

x394

x445

x495

292 x 292Post and Timber

x343

x394Beam and Stringer

x445

x495

Notes:Timbers are surfaced (dressed) and sold green

Source: Canadian Wood Council, Timber http://cwc.ca/wp-content/uploads/Timber.pdfCreated by: Aivars ogla

Moisture ControlThe large size of timbers makes kiln drying impractical due to the drying stresses which would result from differential moisture contents between the interior and exterior of the timber. For this reason, timbers are usually dressed green (moisture content above 19 percent), and the moisture content of timber upon delivery will depend on the amount of air drying which has taken place.[footnoteRef:3] [3: Canadian Wood Council, Timber, Moisture Control - http://cwc.ca/wp-content/uploads/Timber.pdf. Retrieved 16.04.2014]

Likewise dimensional lumber, timber starts to shrink when its moisture content falls below approx. 28 percent limit. The degree of shrinkage depends on the climatic conditions of the environment. For instance, if timber is exposed to the outdoor conditions, then shrinkage is anticipated from 1.8 to 2.6 % in width and thickness (depends on species). Timbers used outdoors, where climate is drier expected shrinkage would be in range of 2.4 to 3.0 % in width and thickness. In either case length changes are negligible.When constructing with Posts and Timbers or Beams and Stringers, allowance should be made for anticipated shrinkage based on the moisture content at the time of assembly. Where the building envelope relies on caulked seals between timbers and other building components, the selection of caulks should take into account the amount of movement which must be accommodated as shrinkage occurs.[footnoteRef:4] [4: IBID]

For a surface of a timber minor checks are common in most service conditions. Therefore an allowance has been made in assignment of working stresses. Checks for columns do not make such an importance, unless there is any signs that there could form a splits or cracks, that could lead to rift (disrupt), dividing column apart. ConclusionIn nowadays wood timbers are less commonly used, because of advantages from other, similar materials. But few of advantages are still helping wood timber as a material, to hold its positions. For example one of the aspects could be fire safety. Timbers, compared to unprotected dimension lumber, offer increased resistance to fire and that leads to fact that timber is often used in Heavy Timber constructions to meet minimum size and fire-resistance rating requirements of building codes. In the United Statesand Canada, timber-frame construction traditions has been restored since the 1970s and is now experiencing a burgeoning renaissance based on ancient skills. Once technologies now are a big part of our life and a heart of all industries, the impact can not be left unmentioned also in building industry. Timber-frame construction has now been modernized with the help of modern industrial tools. These machines and mass-production techniques have led to growth and availability - affordable frames and shorter lead-times for projects.

Preservative-Treated WoodPreservative-treated wood is wood which has been surface coated or impregnated by means of pressure with chemicals which improve resistance to damage from decay and insect attack.[footnoteRef:5] [5: Canadian Wood Council, Preservative treated wood, http://cwc.ca/wood-products/treated-wood/preservative-treated-wood/. Retrieved 18.04.2014]

Preservative-treatment processes do not change the characteristics of wood, but improves quality of material itself, by extending its lifetime and improving severe service conditions. Why wood should be treated?Deterioration of wood in use is commonly caused by decay fungi and certain insects (usually termites and carpenter ants), however other organisms, like marine borers and weather also effects the process. All these aspects can cause a great damage to wood in service.Decay fungi, or wood rotters, are lower forms of plant life related to mushrooms, rusts, molds, and mildews. Wood rotters grow throughout the wood in threadlike strands digesting cellulose and other components for food.[footnoteRef:6] At the beginning it causes a large loss in strength of wood and sooner or later results in soft and crumbly wood. [6: Hoffman T. R., Dr. Hendricks L.T., Powell K., Selecting preservative treated wood with special emphasis on landscape timbers, University of Minnesota, 2002, p.1; ]

The objective of a wood preservative is to preserve wood from the wood destroying agents like fungus or insects, in that way extending the life span of the wood. Specifically getting rid of or avoiding of the fourth condition necessary for fungal growth, the food source. It refers to the treatment of wood using toxic substance, so the fungi are unable to utilize the wood for food. It is probably the most efficient method used today for all types of situations when wood is used in exterior exposed constructions. Objectives of Wood Preservative Treatment1. To increase the wood durability by decreasing the risks of wood destroying agents like fungi, insects and other organisms. It aims in extending the service life of non durable wood.2. To reduce the maintenance and replacement cost of wood after use.

Table 2: Pests and Disease of Wood[footnoteRef:7] [7: Rajendra K.C. An Introduction to Wood Preservative. http://www.forestrynepal.org/images/wood_preservatives_rkc.pdf. Retrieved 18.04.2014]

Wood Inhabiting Fungi:Wood decay, Mold and most sapwood stains are caused by fungi. There are two types of fungi:

1. Wood Destroying Fungi:These are decay fungi that cause Brown rots, White rots and Soft rots.

2. Wood Staining Fungi:Discoloration of wood, it has little or no effects on its strength. They are sap staining fungi, mold fungi etc.

Insects:Several kinds of insects attack wood for shelter and foods. The most important are Termites, Carpenter ants and various Beetles (for example Powdery post beetle, Anobiid beetles), Marine borers etc.

Source: An Introduction to Wood Preservative, Rajendra Kumar KChttp://www.forestrynepal.org/images/wood_preservatives_rkc.pdfCreated by: Aivars oglaCommonly used preservativeThrough experience and experimentation, wood preservatives commonly used today have proved to be highly toxic and hazardous to wood destroying organisms that cause deterioration. Preservatives are generally divided into two categories: oil-type and waterborne salts.Oil-type preservativesBecause oil-type preservatives are insoluble in water, they are resistant to leaching and do not cause wood to swell during treatment. Creosote and pentachlorophenol are the two most commonly used oil preservatives. [footnoteRef:8] [8: Hoffman T. R., Dr. Hendricks L.T., Powell K., Selecting preservative treated wood with special emphasis on landscape timbers, University of Minnesota, 2002, p.4;]

Creosote is a brownish-black oil composed of hundreds of organic compounds. Creosote is usually made by distilling coal oil, but it can also be made from wood or gasoline mixtures. Creosote treating gives wood that brownish to black look, but the main fact is that it is broadly used in treating timbers, piles, poles and crossties.To lower the costs for preservatives creosote is often combined with add mixtures, like coal tar and heavy petroleum oil. However this may decrease the quality of preservative treatment, because adding extra ingredients decreases toxicity to fungi, but in other hand it increases service life because oils and tar helps to reduce weathering and protects material from moisture. Pentachlorophenol, also known as penta or PCP, must be dissolved in petroleum oils or more volatile organic solvents such as mineral spirits, liquefied petroleum gas, and methylene chloride in order to treat wood. Using more volatile solvents will weaken the mixture, by leaving only preservative. Treating solutions normally contain 5% penta by weight.[footnoteRef:9]Pentachlorophenol treated wood will vary from light to dark brown in color depending on the solvent that used. Penta has commonly been used in the millwork industry and for treating posts and poles. [9: Hoffman T. R., Dr. Hendricks L.T., Powell K., Selecting preservative treated wood with special emphasis on landscape timbers, University of Minnesota, 2002, p.4;]

How it is already stated oil-based preservatives include creosote, pentachlorophenol, but few of them, like copper naphthenate, and copper-8- quinolinolate can be divided in specialized oilborne preservative category. Copper naphthenate is safe for use where living plants contact the wood. Copper-8-quinolinolate is unique because it can be applied to food or feed contact surfaces. Elemental copper is an essential element for all known living organisms, including humans and other animals. Copper is normally kept in balance in the human body. Copper compounds are most commonly used in agriculture to treat plant diseases, like mildew, or for water treatment and as preservatives for wood, leather, and fabrics. Food naturally contains copper.[footnoteRef:10] [10: E. Roberts Alley & Associates Inc. Environmental Engineering Consultants. Environmental and Health Risk Evaluation of Copper Naphthenate and Copper Naphthenate Treated Wood. http://www.coppercare.com/Documents/Technical/CuNap_Health_Risk.pdf. Retrieved 18.04.2014]

Waterborne preservativesWaterborne preservatives are primarily inorganic metal systems that include chromate copper arsenate (CCA), copper azole, ammoniacal copper quaternary, copper citrate, and ammoniacal copper zinc arsenate. CCA is by far the most commonly used waterborne system for wood treatment and tends to leave the wood a greenish color. [footnoteRef:11] [11: United Nations Environment Programme. Methyl Bromide Technical Options Committee, Report of the Methyl Bromide Technical Options Committee, UNEP/Earthprint, 2003, p. 302;]

Waterborne preservatives are soluble in water during treatment. Since water is used as a carrier for the chemicals, the wood after treatment should be dried (to a moisture content of 19% or less unless otherwise specified.[footnoteRef:12](Waterborne preservatives are divided into two basic types leach-resistant and leachable. [12: Hoffman T. R., Dr. Hendricks L.T., Powell K., Selecting preservative treated wood with special emphasis on landscape timbers, University of Minnesota, 2002, p.5;]

Leach-resistant preservatives chemically forms insoluble compounds that bond to the wood. Subsequent rewetting of the wood will not cause preservative loss. Leachable compounds do not bond with the wood structure that is why it should not be used in areas of high decay hazard. Two of the most commonly used waterborne salts are chromate copper arsenate (CCA) and ammoniac copper arsenate (ACA). Both substances are leach-resistant and suitable for ground contact.CCA can be defined as a pesticide used to protect wood against decay-causing organisms. This mixture commonly contains chromium (VI) (hexavalent chromium) as chromic acid, arsenic (V) (pentavalent arsenic) as arsenic pent oxide and copper (II) (divalent copper) as cupric oxide, often in an aqueous solution or concentrate.[footnoteRef:13] There are three different types varying in the percentage of these chemicals and they are equally effective and are used to treat lumber, plywood, and timbers. (See table below) [13: Agency for Toxicology and Disease Registry, Division of Toxicology and Environmental Medicine. Chemical-specific health consultation for chromate copper arsenate chemical mixture. http://www.ncbi.nlm.nih.gov/pubmed/18429380. Retrieved 18.04.2014]

Table 3: Percentages of Weight % [footnoteRef:14] [14: Hoffman T. R., Dr. Hendricks L.T., Powell K., Selecting preservative treated wood with special emphasis on landscape timbers, University of Minnesota, 2002, p.5;]

ComponentsType 1Type 2Type 3

Chromium6135.347

Copper1719.619

Arsenic2245.134

Total100.0100.0100.0

Trade namesGreensalt, Langwood, Edalith, TanalithBoliden CCA, Koppers CCA-B, Osmose k-33, Koppers CCA-CWolman CCA, Wolmanac CCA, Chrom-ar-cu

Source: Selecting preservative treated wood with special emphasis on landscape timbersAuthors: Thomas R. Hoffman, Dr. Lewis T. Hendricks, Kevin PowellCreated by: Aivars oglaCCA gives wood a greenish color which with the time weathers to gray, although by approach of new process developed CCA treated wood can be also in brown color.ACA is used for many of the same uses as CCA. Copper and arsenic compounds are dissolved in ammonia. After treatment the ammonia evaporates but leach-resistant copper arsenate remains in the wood. ACA is commonly available in Canada and United States.Three other waterborne preservatives are not so commonly used in treating wood. For example, acid copper chromate (ACC) is a leach-resistant preservative that is used in solutions above ground and for nonstructural items in ground contact. The remaining two - Chromated zinc chloride (CZC) and Fluor chrome arsenate phenol (FCAP) are leachable preservatives that not so effective, but still are adopted in constructions with ground contact or very wet conditions.ProcessMost preservative-treatments are applied using the full-cell pressure method by which wood is placed in a pressure vessel and a vacuum is applied to draw air from the wood cells.[footnoteRef:15] The preservative solution is admitted to the cylinder and is first drawn into the cells by the vacuum. In all treatment methods involving the use of pressure of vacuum it is necessary to place the wood in a pressure vessel, usually known as a cylinder or autoclave. The wood is loaded through a door at one end, usually on railway bogies but sometimes on wheeled baskets, or occasionally loose. (see figure 9.8) Wood impregnation in cylinders can be achieved using a variety of treatment cycles but before discussing these in detail it is necessary to consider the units of pressure and vacuum which are used to describe them. [footnoteRef:16] [15: Canadian Wood Council, Preservative treated wood, http://cwc.ca/wood-products/treated-wood/preservative-treated-wood/. Retrieved 18.04.2014] [16: Barry A Richardson, Wood Preservation, Second Edition, Taylor & Francis e-Library, 2003, p. 76;]

Source: Canadian Wood Council. Wood Reference Handbook, p. 464. Figure 9.8

Pressure of 690 to 1380 kPa (100 to 200 psi) is applied forcing more into the wood preservative. Finally, with last vacuum reoccupy cleaner is removed from the surface of the excess chemicals. To avoid release of excess chemical after treatment, wood in manufacturing premises should be set aside for a time to let chemical to fix into wood cell walls. Once a solid phase over, the waterborne preservative is chemically affixed to the cell walls and material is ready to be used.

Laminated Veneer Lumber (LVL)Introduction Laminated veneer lumber also referred to as LVL is an engineered lumber built up of high grade lumber veneers glued together. The strength properties of LVL enables it to span further and bear greater loads than traditional lumber can with smaller dimensions. It can be used for such things as lintels, columns, beams, truss cords, rafters and formwork. In this chapter we will look into the different aspects of the LVL that will help when making a decision of material in the building process. HistoryLaminated veneer lumber was first used in the production of wooden propellers in World War two airplanes such as the de Havilland Mosquito. It was not until 1970 that the first commercially produced LVL for building construction would be patented as MICRO-LAM laminated veneer lumber. Since then the demand for this structural lumber has grown bring other manufactures to the market under such names as GANG-LAM, STRUCLAM and VERSA-LAM.[footnoteRef:17] [17: Gaspar Lewis & Floyd Vogt, Carpentry 3 Edition by Delmar Copyright 2001 Unit 3 Page 43 ]

SpeciesDouglas fir, Pine and Poplar are commonly used in the product of laminated veneer lumber because of their density and strength properties. It will vary with the location of the producer and what species is assessable to harvest and transport to the factory without great cost. Production This process starts out in the field were lumber is graded and selected by the producer or the forestry service personal in a cut block before harvesting. When the trees are harvested they graded once more and cut to the appropriate length for producing and shipping. At the mill the logs bark is removed and they are then placed up into hot water ponds where they soak for approximately one hour to soften the fibers in the log. With the logs fibers soft it is placed on a large wood lath where the veneers are piled off at a thickness between 2.5mm and 4.8mm[footnoteRef:18] (depending on the manufacturer). The veneers are then graded and sorted for quality and moisture content where they proceed to the dry kilns. From the kiln the Veneers are scanned through an ultrasonic scanner that is able to detect any weakness in the grains of the veneers. Veneers with acceptable but weaker grains will be used on the core where the strongest grains to the outside. A water proof pheno-formalydehyde adhesive resin is applied to both sides of the veneers before they are placed into billets with the grain running length wise. These billets in principle can be endless but are limited by maximum transport lengths. The billet is then rolled through the hot press where microwave heat and pressure is used to bond the billet together to create a large LVL that is then saw into the desired dimensions and treated on the sawn ends. Quality control is then undertaken again using the ultrasonic scanner and various mechanical test to ensure the quality and performance of the engineered product is to the highest standards. Third party quality control is used to ensure the product is worthy of the certification that it has received from the wood council of the countries it is being used in. The LVL is now ready to be ship directly to the contractor, if it was specially order or the building supplier. [18: Canadian Wood Council ,Wood Reference Handbook Page 166 Figure 3.18]

SizesLVLs are produced in large billets normally around 1320mm in width and up to 89mm in thickness which can give a variation of sizes depending on the application it is to be used in. In the chart below the standard sizes that can be found at a supplier are displayed. Table 1: LVL Standard Sizes (inclusive meter price in Danish Krone[footnoteRef:19]) [19: http://www.bygmax.dk/byggematerialer/limtrae/lvl-bjaelker.html Retrieved 16.04.2014]

Size (bxd) in mm45 x 260 - 121.50 DKK pr.m 45 x 300 - 140 DKK pr.m 45 x 360 - 166.50 DKK pr.m45 x 400 187.33 DKK pr.mLengths of up to 20mIf the standard size alone cannot fulfill the static requirements of the building component the LVL can be fastened together according to the manufactures requirements. This also makes it easier for handling and placement on site when the component can be placed in plys and fastened together in place. The following chart shows the number of screws (SDW Structural Wood Screws) to be used when assembling 2 or more LVLs. Table 7[footnoteRef:20] Multi-Ply LVL, PSL and LSL Assemblies [20: http://www.strongtie.com/products/connectors/SDW.asp Retrieved 16.04.2014]

Allowable Uniform Load Applied to Either outside Member

CharacteristicsThe high grade veneers used are low in moisture and free from strength reducing knots making laminated veneer lumber less prone to shrinkage and warping as well as making it stronger, straighter and more uniform than traditional Timber lumber.DurabilityDurability is partly based on the species of wood used to produce the component and although the adhesive used is fully water proof it is not recommended for use with permanent exposer to the elements. If the application of the LVL requires exposer to the elements it is to be special treat after manufactures guidelines, pay special attention to the cut ends and joints. It may also be acceptable to decay if it is located in a high moisture that does not have any ventilation. LVL are not normally treated for pests such as termites so if it is used in an area where pests are a problem it should be treated accordingly.Quality AssuranceThe Laminated veneer lumber is under constant scrutiny right from the start when the tree is harvested through to the production. It is quality controlled at every stage of production for moisture, strength and visual quality. The finish product is controlled with ultrasonic scanners and mechanical tests to ensure that only quality products leave production line. Radom third party test are also run on the product to ensure a non-bios result that ensures the certification of the finished product.[footnoteRef:21] When delivered on site the LVL should be stored flat and of the ground with a cover protecting it from the elements. In cases where there is more than one batons should be laid between each row allowing ventilation around the component. [21: Canadian Wood Council The Design Publications Possibilities of Engineered Wood Products Page 9]

PropertiesDesign Stresses for 2.0E Microllam LVL Modulus of elasticity E 13800 MpaSee annex 1 for all the design Properties to calculate deflections.Density LVL in Douglas fir 552 kg/m3 LVL in Pine 652 kg/m3 LVL in Yellow Poplar554 kg/m3All properties are taken from one manufacturer and should be checked if another manufacture is chosen to deliver the component.[footnoteRef:22] [22: Weyerhaeuser Tru Joist Specifiers Guide TJ-9505 January 2013 Page 4 ]

Fire Laminated veneer lumber reacts similar to solid timber when exposed to fire, with a slow and predictable charring rate. This Predictable charring rate which is established in test and transferred to a chart that can be used to over dimension the component to compensate for the exposer to fire. The higher the fire rating the longer the exposer which leads to more charring thus the beam will be thick and deeper to compensate. Before making these calculation a dialog between the manufactures and local fire authorities should be established to ensure that is carried out to satisfy all.Parallam Strand Lumber (PSL)Parallam strand lumber or PSL made up of the same veneer as the LVL. It is actual a by-product of LVL because the sheets of veneer that meet the strength requirements but have knots or other blemishes are cut into small, long strips used to produce parallam strand lumber. PSL products are controlled with the same quality assurance at the various stages and produced with the same technics as laminated veneer lumber. They share the same characteristics, durability and relation to fire as the LVL, the difference is in the properties of the finish product and the standard sizes.

SizesBeamsWidths in mm 44, 68, 89, 133, 178Depths in mm 241, 281, 302, 356, 406, 483Lengths of up to 20m ColumnsDimensions in mm 89x89, 133x133, 178x178PropertiesDesign Stresses for 2.2E Microllam PSL Modulus of elasticity E 15168 MpaSee annex 1 for all the design Properties to calculate deflections.Density LVL in Douglas fir 610 kg/m3 LVL in Pine 728 kg/m3 LVL in Yellow Poplar536 kg/m3All properties are taken from one manufacturer and should be checked if another manufacture is chosen to deliver the component.[footnoteRef:23] [23: Weyerhaeuser Tru Joist Specifiers Guide TJ-9505 January 2013 Page 4 ]

PriceI consulted with the local building market on the meter price of PSL and I was informed that it is a product that is ordered after application.[footnoteRef:24] [24: Bygma Nyborg Lyvej 7, 5800 Nyborg 88 32 30 00 ]

ConclusionLVL and PSL components offer a strong uniform engineered wood that can be used as beams, lintels, rafters, truss cords and form work. The high quality materials and controlled production gives the components predictable properties that can outperform traditional lumber in span and load baring capacity. LVL would be the most suitable to be used in the rafter framing of the Activity Center in Nab Bay because of the standard measurements, availability, and cost of the product in Denmark compared to PSL wood products. PSL could be considered for beams for example in the ridge but should be compared to glulam beams before making a decision. Laminated veneer lumber products are pushing the limits of what we can do with wood, they enable us to build higher and larger while giving buildings properties that cannot be achieved with other materials. Plywood Plywood is made up mainly soft wood veneers (Douglas fir and Southern pine in structural panels) that are processed in the same way as laminated veneer lumber and graded for moisture, strength and visual aspects. All grades of veneers are used in plywood to produce different grades based on the functional and visual aspects of the finished product. The veneers are placed ninety degrees from one another in layers of odd numbers so that each face of the panel has the grains running length wise. Veneers are bonded with a water proof adhesive under heat and pressure and then finished in various ways depending on the intent for the product.Construction Plywood Plywood that is used in the construction as sheathing that helps stabilize the building structurally and gives a base for the chosen finish. Sheathing normal has a tongue and note on the long axis of the panel to interlock each panel and should be joined over the structure (joist or rafter) on the short axis. These panels finish can from rough to smooth sanded depending on the product that is to be applied to the surface.Sizes Panels are a standard size of 1220mmx2440mm but have different thicknesses that should be chosen from the structural demands of the application and the demands of the finish product being applied to the panel.Standard Thickness and price per panel in Danish Krone[footnoteRef:25] [25: http://www.bygmax.dk/byggematerialer/plader/krydsfiner/tag-og-gulvkrydsfiner.html Retrieved 17.04.2014]

12mm - 189, 50 DKK15mm - 214, 50 DKK 18mm - 248, 50 DKK21mm - 298, 50 DKKSheets also come in 610mmx2440mm for easy handling on site.ConclusionWhen choosing a plywood for the construction the span between the rafters and joist should be looked at to help determine the thickness required. The finishing/covering material should also be considered for the thickness as well as the finish grade of the plywoods surface. Plywood is a strong engineered panel that is produced in an array of types to suit many applications.

Glued laminated timberIntroductionGlue laminated timber also called Glulam, consists of end joining individual pieces of dimensional lumber laminations or boards together with structural adhesives to create long length laminations (span). These long length laminations of timber are then face glued/bonded together with adhesives, side against side, to create the desired glulam piece with different shape and large span.[footnoteRef:26] [26: Gaspar Lewis & Floyd Vogt, Carpentry 3 Edition by Delmar Copyright 2001 Page 52-53]

Types of woodThe majority of the glulam is produced in common spruce, Siberian larch, pine and fir, but there is also focus on combination of wood, such as fir larch, hem fir and spruce pine.Common SpruceThe most common wood used in glulam production is coniferous spruce. Common spruce has good strength quality, light and appearance. That absorbs moisture, dries out relatively slowly and works in case of changes in the moisture.Siberian LarchSiberian Larch grow slowly and the gain width of the wood is therefore narrow, that is due to continental climate in Siberia, where the summer is short - warm and the winter long - cold. This mean a high medium density, which is about 40% higher than common spruce. The prevailing colour of the timber is yellowish-brown or yellowish-grey and sometimes orange, which creates a beautiful and warm play of colours in the wood.PinePine is also used in the production of glulam. This type of wood contains the same good qualities as common spruce. Pine differs from common spruce by its great play of colours. Unlike common spruce and Siberian larch it is possible to pressure-treat pine, because the sapwood has an open porosity. [footnoteRef:27] [27: http://www.lilleheden.dk/uk/glulam.asp?id=2 Retrieved 15.4.2014]

ProcessThe process of glued laminated timber is following the points:[footnoteRef:28] [28: http://www.glulam.co.uk/specGuide_brochure/specGuide04.htm Retrieved 14.4.2014]

1. Laminations are graded to ensure they meet the specified structural grade.2. Timber is kiln-dried to a moisture content of 12% 2% for maximum bond-strength and glulam stability.3. Finger joints are machined and bonded to the appropriate strength grade.4. Finger jointed laminations are planed to required thickness and cut to length.5. Carefully controlled adhesive mix is applied to faces of the lamination.6. Glulam is placed in mechanical or hydraulic systems of the appropriate shape and pressure applied to specification.7. Glulam piece is trimmed to size and the bond strength is tested to specification.8. Cured Glulam member is planed to size and to remove any glue squeezed out in the jigs.9. Any appearance defects, where it is necessary within the grade, the Glulam member is cut, shaped and drilled if required, and any finishing treatments are applied.10. Finished Glulam members are usually wrapped and packed for delivery to site.

Quality Assurance Adjustable - Glulam can be manufactured to the exact dimensions and adjusted as required.Workable - Since glulam is glued together using thin flexible lamination timber it can easily be manufactured in different shapes by preheating and hydraulic system, which is normally expensive in other types of structural materials. This ability gives huge potential for the manufacture of different shape which the architect invents from arches to portal frames. Through the laminating process, a variety of shape can be created ranging from straight rectangular cross-sections to complex curved shapes with varying cross-sections.Durability It is important, such as glulam retain its strength and structural integrity after it has been in service, and, in some cases exposed to exterior conditions under normal conditions of use.[footnoteRef:29] [29: http://www.woodaware.info/PDFs/SCLandGlulam.pdf Retrieved 16.4.2014]

In the open air, under cover and protected against seeping water common spruce and pine is very durable. This is due to the closed cell structure. The common spruce cannot be chemically protected by pressure treatment, because the fluid cannot be pressed into the wood, the rainwater cannot be absorbed as well. Heartwood has natural good duration, whereas the sapwood is easily perishable. With a constructive wood preservative there is a strong possibility that glulam of coniferous trees will have a long duration.The several elements of Siberian larch are hundred years old in Siberia, whick is very durable in a continental climate, cannot be expected to be just as durable in our wet countries, because heartwood-rich pine, which is property surface treated, will be able to pressure-treated pine without soil contact.Fire Resistance Glulam does not burn very well, that can therefore be made extremely fire safe and easily fulfil the standards concerning BD-constructions (fire resistant) set by the authorities.Size Beam: Standard finished widths of glulam members and common widths of the laminating stock they are 80, 89, 130, 140, 175, 184, 225 or 215, 235, 275 or 265, 286, 315 and 365 mm. Single widths of lumber are used for the complete width dimension for members less than 275mm wide. However, members wider than 175 mm may consist of two boards laid side by side. All members wider than 275mm are made from two pieces of lumber placed side by side, with edge joints staggered within the depth of the member. Standard depths for glulam members range from 114mm to 2128mm. A thicker member made laminations costs significantly less than an equivalent smaller member laminations. However, the smaller laminations allow for a greater amount of curvature than thicker laminations. Laminating lumbers may be end jointed into lengths of up to 40m, but the practical limitation may depend on transportation clearance restrictions.[footnoteRef:30] [30: http://cwc.ca/wood-products/glulam/sizes-available/ Retrieved 19.4.2014]

Column: Standard size in mm 65x225-315, 90x225-495, 115x225-495 and 140x225-495. Square column size in mm 140x140, 160x160 and 200x200.[footnoteRef:31] [31: http://www.trada.co.uk/jail/downloads/dir/memberBrochures/8973D4F0-EC05-11D6-864C-00D0B7B8B494/Lilleheden_Glulam_Sizes.pdf Retrieved 19.4.2014]

Strength Glulam is fabricated from many graded lamellas and growth defects in the wood will be minimal during treatment. Therefore glulam has strength, which is proven by many years of experience.Characteristic Strengths (Mpa)Elastic Moduli (Mpa)

GL GradeBendingTension Parallel to GrainShear in BeamCompression Parallel to GrainShort Modulus of Elasticity Parallel to the End GrainShort Duration Modulus of Rigidity for Beams

GL122512.53.72911500770

GL1022113.72610000670

GL819103.7248000530

Table 1: The table show anumbers that are characteristic strength and elastic moduli of glulam beams.[footnoteRef:32] [32: http://www.mcintosh.co.nz/TECHNICAL+INFORMATION/Characteristic+Strengths+and+Elastic+Moduli+for+Glulam+Grades.html Retrieved 19.4.2014]

Density The sorting parameters that companies focuses on are the density and also number/size of knots in the timber. Average density for glulam in common spruce, pine has 460 kg/m and Siberian larch has 650 kg/m.[footnoteRef:33] [33: http://www.lilleheden.dk/uk/glulam.asp?id=2 Retrieved 13.4.2014]

Import Companies is imported the type of engineering wood from selected sawmills in Scandinavia, so raw material is always first quality. All properties are taken from one manufacturer and should be checked if another manufacture is chosen to deliver the component.Conclusion Glulam is abeautiful, strength and flexible material, which can be used in almost all types of buildings and to can be used almost anywhere for many different types of structures, and typically are installed as floor, roof beams, columns, headers over doors and windows, studs in wall framing, bridges, etc.

SteelWhen beginning aproject, we often debate from what materials the project will be made of, whether to usewood, steel or concrete in building. Steel has the perception of strength and endurance. IntroductionStructural steel is a construction material commonly with a profile, formed with a specific shape or cross section, certain standards and mechanical properties. Structural steel is made from organised combination of steel members designed to carry loads and provide adequate rigidity.Advantages[footnoteRef:34] [34: http://www.sals.org.cn/teaching/zhaosir/Introduction-1.pdf Retrieved 19.4.2014]

High strength: The high ratio of strength to weight (the strength per unit weight) Excellent ductility and seismic resistance: Withstand extensive deformation without failure even under high tensile stress Elasticity, uniformity of material: Predictability of properties, close to design assumption Ease of fabrication and speed of erectionDisadvantages[footnoteRef:35] [35: http://www.sals.org.cn/teaching/zhaosir/Introduction-1.pdf Retrieved 19.4.2014]

Susceptibility to corrosion Loss of strength at elevated temperature: Fireproofing costs Susceptibility to buckling: Slender member in compression Fatigue and brittle fractureStructure steel can be used in many types of projects/buildings such as multi-storey and high-rise buildings, buildings of heavy duty plants, tower & mast structures, portal frames, bridges, infrastructures, deployable structures and generalized structures-mechanical.Common shape of steel beam include the IPE, HE A/B, HL, HD sections.Why wood[footnoteRef:36] [36: http://reavesbuildings.com/why-wood Retrieved 19.4.2014]

Wood is more environmentally friendly, constantly growing and is sustainable. Wood in forests, particularly in young vigorous forests, absorbs carbon dioxide, making a growing forest an efficient carbon sink. The forests that are available for timber harvest are large enough to grow wood products to build 1.6 million homes each year, endlessly into the future. Wood is the greenest construction material on the market.Wood buildings have a longer life span than steel building, because Steel sweats causing moisture that provides conditions for mold to grow, which leads to corrosion and rust shortening the longevity of the entire building.Wood, a naturally more efficient insulator than metal, can cut costs on heating and cooling by 30 to 50 percent.Wood retains its structural strength at temperatures higher than 1100 C and its predictable charring rate makes it easy to over dimension to meet fire rating demands, while steel loses 80 percent of its strength at 550CConclusionThe quality of engineered lumber products today gives wood the ability to build higher, wider and heavier than in the past , making it a sustainable alternative to steel in all low rise building applications[footnoteRef:37] [37: http://reavesbuildings.com/why-wood Retrieved 19.4.2014]