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Wood

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Building Materials-Lumber

• Definitions:– Boards: Wooden members less than 1 inch thick.

– Lumber: Wooden members that measure from 1 to 6 inches thick, 2 to 12 inches wide and 6 to 16 feet long.

– Timbers: Wooden members greater than 6 inches thick.

Finished lumber and boards are

sized by “nominal” sizes.

The actual size is less than

the nominal size.

Lumber-cont.

Rough sawn—nominal size

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Finished—Actual size

Wood Terminology

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Wood terms

• Hard wood

• Soft wood

• Heart wood

• Sap wood

• Growth rings

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• Plain (flat) sawn

• Quarter sawn

• Board wood

• Nominal sizing

• Board foot

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• All native species of trees are divided into two classes.

Wood Terminology Hard wood—Soft woods

– Hard wood have broad leaves and are deciduous

– Soft woods are conifers

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Wood Terminology--cont.

Heartwood and sapwood• Sapwood is the outer portion

that conducts sap and has the living cells.

– The thickness will vary, but usually from 1-1/2 to 2 inches on a mature tree.

• Heartwood is the inactive cells in the inner portion.

– Mineral deposits may cause darker color.

– Deposits make wood more durable.

Heart wood

Sap woodBark

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Wood Terminology--cont.

Growth rings• Because the rate a tree grows

change with the seasons, a cross section will show distinctive rings.

• Springwood– Inner part of the growth ring– Usually larger cavities and thin

walls

• Summerwood– Outer part of growth ring– Smaller cells and thicker walls.

• A tree grows one springwood and one summerwood ring each year.

– Used to age trees Springwood

Summerwood

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Wood Terminology--cont.

Sawing Direction

• Plain sawn (Flat sawn)– Board is sawed “parallel” to growth rings

– Most common boards.

• Quarter sawn– Log is first quartered

– Boards are cut “perpendicular” to the grain.

– Usually must be special ordered.Were have you seen quarter sawn boards used?

Wood Terminology--cont. Nominal sizing

• Dimensioned finished lumber is sized using what is called an nominal sizing.

• The nominal size is not the finished size of the lumber—it is the rough cut size.

• The finished size, what you buy, is always less than the rough cut size.

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Lumber Sizes

Rough Size (in)

Actual Size (in)

Board Feet per Foot of

Length

1 x 4 3/4 x 3-1/2 1/3

1 x 6 3/4 x 5-1/2 1/2

1 x 8 3/4 x 7-1/4 2/3

1 x 10 3/4 x 9-1/4 5/6

1 x 12 3/4 x 11-1/4 1

2 x 4 1-1/2 x 3-1/2 2/3

2 x 6 1-1/2 x 5-1/2 1

2 x 8 1-1/2 x 7-1/4 1-1/3

2 x 10 1-1/2 x 9-1/4 1-2/3

2 x 12 1-1/2 x 11-1/4 2

4 x 4 3-1/2 x 3-1/2 1-1/3

6 x 6 5-1/2 x 5-1/2 3

Cut Size — Actual Size

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Softwood Construction Lumber Standard

DimensionsThickness (inches) Width (inches)

Nominal Dry

1 3/4

1-1/4 1

1-1/2 1-1/4

2 1-1/2

2-1/2 2

3 2-1/2

3-1/2 3

4 3-1/2

1/2 4

5+ 1/2 “ less

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Wood Terminology--Board Foot

• In a store lumber, boards and timbers are usually sold as $/piece, but the listed price is based on a $/bf.

• Large volumes of lumber can also be purchased on a $/bf bases.

• Board foot is a volume measurement.

• Board foot is calculated using the nominal size, not the actual size.

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Wood Terminology--cont.Board Foot

€

Bf = ( ) ( ) ( )length ft x width in x depth in

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or

Bf = ( ) ( ) ( )length in x width in x depth in

144

Equations:

• A board foot is a volume of lumber for a board that is one (1) inch thick, twelve (12) inches wide and twelve (12) inches long.

• One board foot = 144 in3

• Nominal sizes are used to calculate board feet when calculating costs.• Actual sizes are used when calculating loads or strength.

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Wood Terminology--cont.Board Foot Example

• Determine the number of board feet for the following list of dimensioned lumber.– 2 - 2 x 4 x 12– 3 - 1 x 4 x 10– 2 - 4 x 4 x 8

€

Bf = ( ) ( ) ( )length ft x width in x depth in

12

= 2 x12 4 2x x

12= 16 Bf

= 3 x10 4 1x x

12= 10 Bf

= 2 x8 4 4x x

12= 21.33 Bf

€

16 + 10 + 21.33 = 47.33 Bf

Wood Characteristics

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Eight (8) Characteristics of wood

1 Defects

2 Grain orientationa) Stiffnessb) Load bearing capabilitiesc) Fastener holding ability

3 Ease of working4 Paint holding ability5 Decay resistance

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Characteristics—Defects--Structural

Cross grain crack

Shake

Wane (Bark)

Split

Sloping grain

Knot

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Characteristics—Defects--Dimensional

Characteristics—Grain Orientation

• Grain orientation is important for three reasons.1 The direction of the grain affects the amount of deflection that

occurs when loads are applied.

2 Load bearing ability.

3 The orientation of fasters with the gain can increase or decrease splitting when installing fasteners.

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Characteristics - Grain Orientation - Stiffness

• Stiffness is a measure of the amount of deflection that occurs when a load is applied.

• The amount of deflection for a load is determined by the dimensions of the member and the grain orientation.

• Amount of acceptable deflection is different for each building member.

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Characteristics - Grain Orientation -- Load Bearing

Wood is stronger when forces are applied parallel to the grain than when force is applied perpendicular to the

grain.

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Characteristics – Load Bearing – cont.

Load bearing ability of wood is determined by 6 additional factors.

1. Number of defects

2. Size of defects

3. Type of defects

4. Location of defects

5. Species

6. Density and moisture content

Characteristics - Grain Orientation - Splitting

Fasteners installed parallel to the grain of the wood will increase the chance of splitting the wood compared to fasteners installed perpendicular to the grain of the wood.

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Wood Characteristics-cont.

• Ease of working– Tree species vary on workability and machineability.

• Paint holding ability– Paint holds better on edge grain that on flat train– Knots do not hold paint well– The bark side of a flat sawed board will usually hold paint

better than the inner side.

• Decay resistance– Wood that is continuously dry or continuously wet does not

decay.– Ideal decay conditions are 21-24% moisture– The heartwood of some species is very decay resistant.

Summary Tables of Characteristics.

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Wood CharacteristicsSoft Woods

Charact eri sti c St rengt h

Kind of Woo d Eas e of Work ing

Paint Holding

Na il Holding

Heartw oo d Dec ay

Resist anc e Bending Sti f fn ess

Sof t woo ds

Cedar, inland red B A C A C C

Cedar, west ern red A A C A C C

Fir, Douglas C C B B A A

Fir, white B B C C B B

Hemlock, west ern B B B C B A

Larch, west ern C C A B A A

Pine, west ern white A A A B B B

Pine, lodge pole A A B B B B

Pine, Ponde rosa A B B B C C

Pine, South ern yell ow C C A B A A

Pine, sugar A A A B C C

Redwood B A B A B B

Spruce, Engelmann B B C C C C

Spruce, Sitka B B C C B A

Tamarack C B B B B B

Structures and Environment Hand Book, MWPS-1

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Wood CharacteristicsHard Woods

Charact eristi c St rengt h

Kind of Woo d Eas e of Work ing

Paint Holding

Na il Holding

Heartw oo d Dec ay

Resist anc e Bending Sti f fn ess

Hardwoods

Ash, white C C A C A A

Birch, yell ow C B A C A A

Cot to nwood B B C C C B

Elm, rock C C B B A A

Hickory, t rue C C A C A A

Maple, hard C B A C A A

Oak, red o r white C C A A A A

Walnut B C B A A A

Structures and Environment Hand Book, MWPS-1

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Selecting Wood For Common Home and Farm Use

(Fact Sheet F903)

Concrete Forms Good stiffness, easy to nail and cut, resists bending, warping, or splitting during installation and reuse

Exposed Platforms and Porches

High decay resistance, good stiffness and strength, good wear and splinter resistance.

Feed Racks and Feed Bunks

Hardness and freedom from splitting, medium decay resistance, ease to work.

Fence Posts High decay resistance and little or no sapwood for untreated posts, good bending strength, straightness, and high nail holding.

http://ohioline.osu.edu/for-fact/pdf/0009.pdf

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Selecting Wood For Common Home and Farm Use--cont.

(Fact Sheet F903)

Flooring and Steps Good decay resistance, wear resistant, and resists warping and shrinking.

Framing, Joists, Rafters, etc.

High strength properties in stiffness, hardness, and bending, good nail, screw, and glue holding properties, free of warp and medium weight.

Gates and Fences Good bending strength, decay resistant, paints well, holds nails, resists weathering, free of warp and splitting, lightweight.

House Trim For exterior uses look for woods that are decay resistant with good painting and weathering characteristics, is easy to work and resists warping and shrinking, good nail holding ability and easy to work.

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Selecting Wood For Common Home and Farm Use--cont.

(Fact Sheet F903)

Poles and Posts for Pole Barn Construction

High stiffness and strength, free of crook, minimum taper, good nail holding qualities, decay resistance.

Pressure treat poles and posts in direct ground contact.

Posts and Beams for Post and Beam Barn Construction

High stiffness and strength, easy to work, moderate weight, and free of crook.

Roof Boards Good nail or screw holding properties, easy work, low shrinkage, high stiffness and free of warp, free of splits.

Scaffolding High bending strength, high stiffness, high nail holding, medium weight, and free of compression failures and cross grain.

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Selecting Wood For Common Home and Farm Use--cont.

(Fact Sheet F903)

Shelving Good stiffness and free of warp with good finishing properties.

Siding Good paintability, good weathering qualities, decay resistant and resistant to warp and shrinkage.

Storage Bins, Tanks, Vats, etc.

High decay resistance and low shrinkage.

Studs and Plates Medium stiffness and strength, good nail holding, medium free of warp, and moderately easy to work.

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Pressure Treated Wood

• Pressure treating is a process that forces a chemical preservative deep into the wood.

• Chemicals– Until 2004, the preservative most commonly used in residential

pressure-treated lumber was chromated copper arsenate (CCA).• Lumber or poles light green in color• Now limited to commercial uses.

Pressure Treatment-cont.

• Ammoniacal cooper zinc arsenate (ACZA)– Primary marine use

– Olive to bluish green

• Alkaline copper quat (ACQ) – Many variations

– Not standardized for marine applications

– Dark greenish brown color

• Copper azone (CBA)– Several variations

– Light brown color

• Borate preservatives– Several different salts

– Effective, but preservatives are water soluble

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Approved chemicals for residential use:

• Creosote- Oil based- No exposure to humans

or animals- Dark brown black color

• Pentachlorophenol- Oil based- No direct contact with

humans or animals- Not resistant to marine

borers- Light brown to dark

brown color depending on the oil used

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Questions