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.
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Lumber-cont.
Rough sawn—nominal size
Finished—Actual size
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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
• Board foot
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Wood Terminology
Hard wood—Soft 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.
Sap wood
Bark
– 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
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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
Summerwood
– 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
Were have you seen
quarter sawn boards
used?
– Boards are cut “perpendicular” to
the grain.
– Usually must be special ordered.
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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 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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Cut Size — Actual Size
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
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Softwood Construction
Lumber Standard
Dimensions
Thickness (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
• 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.
Bf =
Equations:
length (ft) x width (in) x depth (in)
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or
Bf =

length (in) x width (in) x depth (in)
144
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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
– 2-4x4x8
length (ft) x width (in) x depth (in)
12
12 x 4 x 2
= 2 x
 16 Bf
12
10 x 4 x 1
= 3 x
 10 Bf
12
8 x 4 x 4
= 2 x
 21.33 Bf
12
Bf =
16 + 10 + 21.33 = 47.33 Bf


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Wood Characteristics
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Eight (8) Characteristics of wood
1
2
Defects
Grain orientation
a)
b)
c)
3
4
5
Stiffness
Load bearing capabilities
Fastener holding ability
Ease of working
Paint holding ability
Decay resistance
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Characteristics—Defects-Structural
Wane (Bark)
Knot
Shake
Split
Cross grain crack
Sloping grain
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Characteristics—Defects-Dimensional
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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
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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.
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Summary Tables of
Characteristics.
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Wood Characteristics
Soft Woods
Charact eri sti c
St re ngt h
Eas e of
Work ing
Paint
Hol ding
Na il
Hol ding
He artw oo d
Dec ay
Resist anc e
Bending
Sti f fn ess
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, western white
A
A
A
B
B
B
Pine, lodge pole
A
A
B
B
B
B
Pine, Ponderosa
A
B
B
B
C
C
Pine, Southern yell ow
C
C
A
B
A
A
Pine, sugar
A
A
A
B
C
C
Redwo od
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
Kind of Woo d
Sof t woo ds
Structures and Environment Hand Book, MWPS-1
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Wood Characteristics
Hard Woods
Charact eri sti c
St re ngt h
Eas e of
Work ing
Paint
Hol ding
Na il
Hol ding
He artw oo d
Dec ay
Resist anc e
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, r ock
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
Kind of Woo d
Bending
Sti f fn ess
Ha rdw oods
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.
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Pressure Treatment-cont.
Approved chemicals for residential use:
• 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
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
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