Dressed sizes of sawn lumber are given in the grading rules of agencies that formulate and maintain such rules and in Table 10.3. The nominal and dressed sizes are developed in accordance with the American Softwood Lumber Standard, Voluntary Product Standard PS 20-94. These sizes are generally available, but it is good practice to consult suppliers before specifying sizes not commonly used to find out what sizes are on hand or can be readily secured.
The supplement to the National Design Specification for Wood Construction published by the American Forest & Paper Association (formerly the National Forest Products Association) presents tables of section properties of standard dressed sawn lumber and glulam timber. Standard finished sizes of structural glulam timber should be used to the extent that conditions permit. These standard finished sizes are based on lumber sizes given in Voluntary Product Standard PS 20-94. Other finished sizes may be used to meet the size requirements of a design, or to meet other special requirements.
For the manufacture of glulam nominal 2-in-thick lumber, surfaced to 13â„8 in or 11â„2 in before gluing, is used to laminate straight members and curved members having radii of curvature within the bending-radius limitations for the species. Nominal 1-in-thick lumber, surfaced to 3â„4 in before gluing, may be used for laminating curved members when the bending radius is too tight to permit use of nominal 2- in-thick laminations. Other lamination thicknesses may be used to meet special curving requirements.
Standard sizes and grades of structural panels are given in U.S. Product Standard PS 1-95 for Construction and Industrial Plywood and Performance Standard for Wood-Based Structural-Use Panels, Voluntary Product Standard, PS 2-92. See also Art. 10.12.
Weight and Specific Gravity. Specific gravity is a reliable indicator of fiber content.
Also, specific gravity and the strength and stiffness of solid wood or laminated products are interrelated. See Table 10.4 for weights and specific gravities of several commercial lumber species.
