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Wood

Wood. 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.

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Wood

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  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. Finished—Actual size Rough sawn—nominal size

  4. Wood Terminology

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

  6. Wood TerminologyHard 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 • Boards are cut “perpendicular” to the grain. • Usually must be special ordered. Were have you seen quarter sawn boards used?

  10. 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.

  11. Cut Size — Actual Size

  12. Softwood Construction Lumber Standard Dimensions

  13. 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.

  14. 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:

  15. 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

  16. Wood Characteristics

  17. Eight (8) Characteristics of wood • Defects • Grain orientation • Stiffness • Load bearing capabilities • Fastener holding ability • Ease of working • Paint holding ability • Decay resistance

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

  19. Characteristics—Defects--Dimensional

  20. Characteristics—Grain Orientation • Grain orientation is important for three reasons. • The direction of the grain affects the amount of deflection that occurs when loads are applied. • Load bearing ability. • The orientation of fasters with the gain can increase or decrease splitting when installing fasteners.

  21. 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.

  22. 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.

  23. Characteristics – Load Bearing – cont. • Load bearing ability of wood is determined by 6 additional factors. • Number of defects • Size of defects • Type of defects • Location of defects • Species • Density and moisture content

  24. 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.

  25. 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.

  26. Summary Tables of Characteristics.

  27. Wood CharacteristicsSoft Woods Structures and Environment Hand Book, MWPS-1

  28. Wood CharacteristicsHard Woods Structures and Environment Hand Book, MWPS-1

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