Wood

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Wood
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Building Materials-Lumber

• Definitions
• Lumber Wooden members that measure from 1 to 6
  inches thick, 2 to 12 inches wide and 6 to 16
  feet long.
• Boards Wooden members less than 1 inch thick.
• Timbers Wooden members greater than 6 inches
  thick.

• Finished lumber and boards are sized by nominal
  sizes.
• The actual size is less than the named size.
• Rough sawn lumber and boards will be closer to
  actual size, but the surfaces will be irregular.

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Wood Terminology
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Wood terms

• Hard wood
• Soft wood
• Heart wood
• Sap wood
• Growth rings
• Plain (flat) sawn
• Quarter sawn
• Board wood
• Nominal sizing

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Wood Terminology Hard woodSoft woods

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

• 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.

Sap wood
Bark
Heart wood
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Wood Terminology--cont. Growth rings
Summerwood

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

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Cut Size Actual Size
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Softwood Construction Lumber Standard Dimensions
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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

• 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.

Equations
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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

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Eight (8) Characteristics of wood

• Defects
• Grain orientation
• Stiffness
• Ease of working
• Paint holding ability
• Nail holding power
• Decay resistance
• Bending strength

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Wood Terminology--contDefects
Wane (Bark)
Knot
Shake
Split
Cross grain crack
Sloping grain
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Wood Terminology--contDefects
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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.
• Nail holding power
• Related to density and its splitting tendencies
• Denser and harder woods hold better if they do
  not split.
• 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.

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Wood Characteristics-cont. Bending strength

• Bending strength is determined by 6
  characteristics.
• Number of defects
• Size of defects
• Type of defects
• Species
• Density and moisture content
• Grain orientation

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Grain Orientation
Wood is stronger when forces are applied parallel
to the grain than when force is applied
perpendicular to the grain.
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Wood Characteristics-cont Stiffness

• Stiffness is a measure of the amount of
  deflection that occurs when a load is applied.
• Determined by the cross section shape of the
  member and the load.
• Amount of acceptable deflection is different for
  each building member.

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Summary Tables of Characteristics.
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Wood CharacteristicsSoft Woods
Structures and Environment Hand Book, MWPS-1
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Wood CharacteristicsHard Woods
Structures and Environment Hand Book, MWPS-1
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Selecting Wood For Common Home and Farm Use
(Fact Sheet F903)
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)
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Selecting Wood For Common Home and Farm
Use--cont. (Fact Sheet F903)
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Selecting Wood For Common Home and Farm
Use--cont. (Fact Sheet F903)
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Pressure Treated Wood

• Pressure treating is a process that forces a
  chemical preservative deep into the wood.
• Chemicals
• Until 2003, the preservative most commonly used
  in residential pressure-treated lumber was
  chromated copper arsenate (CCA).
• Now limited to commercial uses.
• Recommended chemicals for residential use
• Amine copper quat (ACQ)
• Copper azone (CA)

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Questions