1. Wood

2. 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.

3. Lumber-cont.
Rough sawn—nominal size
Finished—Actual size

4. Wood Terminology

5. Wood terms Hard wood Soft wood Heart wood Sap wood Growth rings
Plain (flat) sawn
Quarter sawn
Board wood

6. 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

7. 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

8. 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

9. 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
Usually must be specially ordered.

10. Wood Characteristics

11. Five (5) Characteristics of wood
Defects
Grain orientation
Ease of working
Paint holding ability
Decay resistance

12. Characteristics—Defects-- Structural
Wane (Bark)
Knot
Shake
Split
Cross grain crack
Sloping grain

13. Characteristics—Defects-- Dimensional

14. 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.

15. 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.