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Wood Classes
- Softwood, predominatly evergreens, cone-bearing trees, pines, firs, hemlocks
- Hardwood, broad-leaf, flowering trees, cherry, maple, oak
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Wood composition
- Non-homogeneous organic material
- High shrinkage and swelling across grain
- Low shrinkage and swelling along grain
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Plain Sawn
Cut similar to meat, parallel layers, least expensive, tends to twist and cup, varied grain
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Quarter Sawn
Wood is cut at right angles, most expensive, uniform grain
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Wood Defects
- Knots – hard nodes of branches
- Checks – splits across the annual rings
- Shanks – splits between annual rings
- Pitch pockets – well-defined openings between annual rings containing solid or liquid pitch
- Wane – presence of bark or absence of wood along edge
- Cupping – curvature across face
- Crook (Crown) – curvature along edge
- Bow – curvature along length
- Twist – edges turning in opposite direction
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Lumber
- Board - less than 2" thick and more than 2" wide (siding, interior trim)
- Dimensional lumber - 2"-4" thick and more than 2" wide
- Timber - 5" and more in the least direction (beams, posts)
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