Dressed Size
Dressed size is the actual finished dimension of lumber after it has been surfaced (planed) from its rough-sawn state. Dressed sizes are always smaller than nominal sizes because surfacing removes material. For softwood, dressed sizes follow standardized reductions codified in PS 20; for hardwood, standard surfaced thicknesses depend on the rough quarter-system thickness.
In-Depth Explanation
Dressed size is what you actually measure when you put a tape on the board after surfacing. For softwood dimensional lumber, the American Softwood Lumber Standard (PS 20) establishes exact dressed dimensions for each nominal size: a nominal 2-inch dimension dresses to 1-1/2 inches when dry (or 1-9/16 inches when green), and a nominal 6-inch width dresses to 5-1/2 inches when dry. For hardwood lumber, the NHLA establishes standard surfaced thicknesses from each quarter-system rough thickness: 4/4 (1 inch rough) dresses to 13/16 inch, 5/4 (1-1/4 inch rough) dresses to 1-1/16 inch, 6/4 (1-1/2 inch rough) dresses to 1-5/16 inch, and 8/4 (2 inches rough) dresses to 1-13/16 inch. These dressed dimensions allow enough material for the buyer to do a final light sanding or pass and achieve common finished thicknesses of 3/4 inch, 1 inch, 1-1/4 inches, and 1-3/4 inches respectively. Understanding dressed sizes is essential for accurate project planning and material estimation.
Usage Example
The architect specified dressed size dimensions in the framing plan, noting 1-1/2 x 5-1/2 inches rather than the nominal 2x6 to ensure accurate structural calculations.