A WOOD MATERIALS (A) ( ^[5]) ( ^[15]) ( ^[16]) ( ^[17]) ( ^[26]) ( ^[41]) ( ^[50]) ( ^[60])

1. General ( Note: See p. 362 for species table. See pp. 337 341 for nails and connectors.)

   1. Two general types of wood are used in buildings:

      1. Softwood (from evergreen trees) for general construction

      2. Hardwood (from deciduous trees) for furnishings and finishes

   2. Moisture and shrinkage: The amount of water in wood is expressed as a percentage of its oven-dry (dry as possible) weight. As wood dries, it first loses moisture from within the cells without shrinking; after reaching the fiber saturation point (dry cell), further drying results in shrinkage. Eventually wood comes to dynamic equilibrium with the relative humidity of the surrounding air. Interior wood typically shrinks in winter and swells in summer. Average equilibrium moisture content ranges from 6% to 11%, but wood is considered dry enough for use at 12% to 15%. The loss of moisture during seasoning causes wood to become harder, stronger, stiffer, and lighter in weight. Wood is most decay-resistant when moisture content is under 20%.

2. Lumber

   1. Sizes

      1. Sectional

         Nominal sizes	To get actual sizes
         2 's up to 8 's	deduct ?
         8 's and larger	deduct ?

      2. Lengths

         1. Softwoods: cut to lengths of 6 ? to 24 ?, in 2 ? increments

         2. Hardwoods: cut to 1 ?-long increments

   2. Economy: best achieved when layouts are within a 2