constructing concrete forms course

8/19/2019 Constructing Concrete Forms Course

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Constructing ConcreteForms and Reinforcement

The National Association of

Certied Home Inspectors


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Definitions of terms associated

with form construction:• Footer form (footing) - a continuous slab of concrete that

provides a solid, level foundation for block and other masonry.

• Construction joint - place here one pouring of concrete stops

and another starts. !lso called a "cold joint#.• Control joint - planned break hich permits concrete to e$pand

and contract ithout cracking.

• %einforced concrete - concrete slabs or structures that are

strengthened ith embedded steel rods or ire mesh.

• &ale - a heavy plank e$tending along the sides of ooden

concrete forms for reinforcement of the ' $ studs.


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Selecting materials for concrete

forms. • *etal forms

• +ynthetic materials

• &ood (most commonly used). t should be straight,sound lumber, free of knots, decay and other defects.

Commonly, forms are steel framed plyood.


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Well constructed concrete forms

should be:• +ubstantial enough to retain their correct shape hen filled.

Freshly mi$ed concrete e$erts great pressure since concrete

eighs from / to 0/ lbs. per cubic foot.

• 1ight to prevent the escape of the ater-cement paste, becausethe loss of ater ill change the strength of the remaining

mi$ture.

• Constructed so they can be easily filled from a truck or

heelbarro.

• 2asily removed after the concrete has hardened.


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Construction of forms.

• 3se soft, clean, straight lumber.

– $ 3se spruce ' $ or ' $ 4 for form because it ill not arp as bad as yello pine.

– $ 3se green lumber hen possible because it does remove the ater from the freshconcrete like kiln dried lumber ill.

• +harpen stakes evenly so they can be driven in straight.• 5lace stakes about / inches apart along the outside of the form for inch thick

concrete. 5lace the stakes close hen the concrete is more than inches thick.

• 3se a transit or level to adjust the height of forms for the desired slope or fall of

the slab.

• 6rive nails through the form and into, but not through, the stakes.

• 7e sure the stakes do not stick up above the top of the form. f they do, sathem off so they are level ith or tapered don from the form.

• For smooth alls use plyood panels.


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Form 8ayout


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Types of points.• solation joints

9 3sed to separate floors from points of abutment ith alls

columns, or building footings.

• Control joints

9 *ay be properly called crack control joint.

• 1o prevent random cracking, predetermine the crack location by

making a crack control joint or by saing into the floor to make a

eakened plane so that the crack ill occur here you ant it.

• Construction joints

9 Created here concrete stopped and later as started again.

9 *ost construction joints are actually a combination of a control

joint and a construction joint.


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Corner 8ayout


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Forming the :utside &all


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Forming the nside &all


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Types of reinforcement

• +teel bars

9 +teel reinforcing bars have ridges that increase the bond beteen the

concrete and the steel.

9 7ars may be ordered by number or by diameter. t is available in

diameters from ; to inch and over. 1hey may be purchased in '/,/, or 4/ foot lengths.

9 1he si


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Types of reinforcement

• &elded ire fabric

9 =enerally available in a 4 by 4 inch pattern and consist of number 4, >, or /

gauge ire.

9 3sed for jobs re?uiring relatively light reinforcement.

9 3sed to help reduce the cracking due to changes in temperature and moisture in

the concrete. 9 %einforcement ire fabric needs to be placed so it is protected by an ade?uate

coverage of concrete.

9 8ap elded ire a minimum of inches or at least one full spacing plus to

additional inches.

• Fiberglass fibers

9Fibers may be mi$ed in concrete mi$tures for increased tensile strength.

9 7y using the fibers in the mi$ture the fibers are mi$ed completely from the top to

the bottom of the slab.

9 Cost is comparable to the price of elded ire fabric.


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Form 5anel 6etails


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Form 5anel +i


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Footings and foundations

• o substitute for an ade?uate foundation, hich is the key part

of every building.

• !de?uate footing provides a stable base and directly affects

both the life and performance of the building.• 5rotects against rats, mice termites, ater and the elements.

• Foundation consists ofD

9 ts bed, ith the earth giving support

9 ts footing, the idened part of the structure resting upon the bed

9 ts all, the structural part resting upon the footing.

• 1he si


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oad!carrying capacities of Soils

Type of soil Tons per s". ft.

+oft clay 1

Firm clay or fine sand 2

Compact fine or loose coarse sand 3

8oose gravel or compact coarsesand

4

Compacted sand-gravel mi$ture 6


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• !ppro$imate ratio of foundations si


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Care of concrete forms

• Forms should be coated ith used motor oil.

• 3se paraffin oil diluted ith kerosene or ben


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#. Sta$e %.

Tie& Snap

'. 'race (.

Spreader

C. Tie& )* + ,* -.

Tie& Wire

D. Sheathing .Footing

Constructed

&ooden Forms

Custom made and

used for certaincustom foundation

ork.


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oints Commonly

3sed in Concrete Construction


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Control Eoints


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%einforcing !ffectsD +trength of Concrete

+tructuresD %einforce Concrete to ncrease 1ensile +trength


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Reinforcing For Concrete

+teel

%einforcing 7ars (%e-%od)'/ 8engths

+i


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Reinforce For Concrete

&ire Fabric *esh

0 H 0/ %olls 4 H 4 /, >, 4 I =age H , / I =age

1 1ensile +trength nstallation

4/,/// - B/,// 5+ :verlap mesh plus

'

inches


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Concrete is strengthened greatly by the addition of

steel rods or wire mesh


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Footing rebar must be laid in

such a manner as to allo for

concrete movement.

2nds are tied, not continuous

or elded.

nterior and e$terior rebar

should e$change at corners

ntersections should e$tend to

the e$terior


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The footer should be as thic$ as the wall resting on it is wide.

The footer should also be at least twice as wide as the wall.

Concrete footers are placed below the frost line to pro4ide a

solid base for masonry walls.

constructing concrete forms course

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