Chapter 2

1. Chapter 2 Lumber

2. Manufacture of Lumber • Logs arrive at a sawmill and the bark is removed. • A bandsaw cuts the log into planks. • A series of saws are used to slice, edge and trim. • The wood is cut to various dimensions. • Wood is stacked with stickers to dry.

3. Manufacture of Lumber (cont.) • Lumber is standardized and shipped. • Measuring terms Edge – long, narrow surface of board Side – long, wide surface of board Ends – the cross sectional extremes of board Thickness – narrow distance across the end Width – distance across the side Length – distance from end to end

5. Plain-Sawed Lumber • Common way of cutting lumber. • Log is cut tangent to annular rings. • This produces a distinctive grain. • Least expensive, producing greater widths. • Shrinks and swells unevenly, tends to warp. • Sometimes called slash-sawed.

6. Plain Sawn

7. Quarter-Sawed Lumber • Produces pieces with annular rings at right angles. • Shrinks evenly, warps less easily. • High durability. • Frequently used for flooring. • Also called vertical-grain or edge-grain.

8. Quarter Sawn

9. Combination Sawing • Process of varying the cutting styles to produce a mixture of plain and quarter sawn lumber. • More efficient use of materials.

11. Moisture Content and Shrinkage • Green Lumber • Water fills the wood cell tubes. • Newly cut wood that hasn’t dried and will shrink. • As it shrinks, it usually changes shape. • Subject to decay due to its moisture content.

13. Moisture Content and Shrinkage • Seasoned Lumber • Lumber that has been dried. • Should be protected from moisture.

14. Moisture Content (MC) • Expressed as a percentage. • Determined by the weight of water removed by oven drying and dividing that number by the dry weight. • Example – if a wood sample is 16 ounces wet and 13 ounces dry, then

15. Drying Lumber • Lumber is air dried by stacking in piles with stickers between layers. • Later it is moved into huge ovens called kilns that provide controlled temperatures, humidity and air circulation. • Kiln drying speeds up the drying time but is more costly.

18. Drying Lumber (cont.) • Recommended MC • Framing lumber less than 19% • Exterior finish lumber – 12% • Interior trim and cabinet work – 8-10% • Moisture meters are used to measure moisture content.

19. Lumber Storage • Store lumber so it is protected from moisture and other hazards. • Keep lumber off the ground. • Cover with a tarp, leaving room for air circulation.

20. Lumber Defects • A defect is any fault that detracts from its appearance and strength. • Warps are caused by drying lumber too fast, poor storage, or surfacing lumber before it is dry. • Splits and checks are caused by uneven drying. • Shakes run parallel to annular rings.

22. Lumber Defects (cont.) • Lumber with high percentage of juvenile wood tends to warp and twist more. • Knots are cross-sections of branches in the trunk of the tree. • Pitch pockets are small cavities holding pitch.

23. Lumber Defects (cont.) • Wane is bark on the edge of lumber. • Pecky wood has small grooves through the grain.

24. Board defect types

25. Lumber Grades and Sizes • Largest manufacturer of softwood is Western Wood Products Association (WWPA). • Hardwood grades established by the National Hardwood Lumber Association.

26. 1x6 2x6 4x6 Softwood Lumber Grades • Three general categories • Boards – 1 inch or less in thickness i.e. 1x6 • Dimension Lumber – 2 inches in thickness i.e. 2x6 • Timbers – larger than 2 inches in thickness i.e. 4x6

27. Hardwood Lumber Grades • Firsts and seconds (FAS) is the best grade. • Each piece must be at least 6” wide by 8’ long. • Next best grade is called Select. • No. 1 common grade allows narrower widths and shorter lengths.

28. Lumber Sizes • Rough lumber that comes directly from the sawmill is close to nominal size. • Planing reduces the thickness and width to standard and uniform sizes. • Nominal size – what the piece is called • Actual size – the actual measurements

29. Lumber Sizes (cont.) • Lumber sizes are indicated by a series of numbers. • Thickness” × Width” × Length’ • For example, 1” × 10” – 12’ • One inch thick × 10 inches wide and 12 feet long

30. ` 2″ 2x6 6″ Actual vs. Nominal • Actual dimensions of lumber are smaller than the name implies. • For example: • Nominal 2 x 6

31. Actual vs. Nominal • Actual 1½” x 5½” ` 2x6 1½″ 5½”

33. Board Foot Measure • Lumber may be purchased by the piece. • i.e. 36 – 2x8 –16′ • Large quantities of lumber are often purchased by the board foot (bdft). • i.e. 750 bdft of 2x4’s • This is typically done at the wholesale level. • Also allows purchasing of varying board sizes.

34. 1 foot 1″ 12″ Board Foot Measure (cont.) • Board foot measure refers to a volume of wood. • It is defined as the volume of wood measuring 1” × 12” × 1’ • One board foot may have many shapes.

36. BDFT Calculations (cont.) Formula for figuring board feet is: Bdft = # pieces × Thickness″ × Width″ × Length′ ÷ 12 Note: Thickness (inches), Width (inches), & Length (feet) Example – How many board feet are in 180 pieces of 2x816′ long? 180 × 2 × 8 × 16 ÷ 12 = 3840 bdft

37. Conclusion • Lumber is plain sawn or quarter sawn. • Moisture content of wood is important. • Wood can be air dried or kiln dried. • Defects affect appearance and strength. • There are many different grades of wood.

38. Conclusion (cont.) • Nominal size is not the same as actual. • Board foot is a measure of wood volume.