In most cases, hardwood boards come in random widths to be ripped to size by the woodworker. For instance, hardwood trim that ends up being just over 1" thick (surfaced on 2 sides) is called a five-quarter (5/4) board. In North America, hardwood lumber is usually specified using the quarter system, where a board is identified by its thickness in quarters of an inch. Surfaced refers to a finishing process that smooths the lumber to remove all saw marks. Hardwood lumber is sized based on how many sides are surfaced. According to NIST Publication P20, actual lengths must be at least equal to the nominal length, but can be up to 3" longer than the nominal length. Softwood lumber comes in a number of standard lengths as listed in the table below. North American Standard 8-by Timber (Surfaced 4 Sides, S4S) NOMINAL SIZE (INCHES) North American Standard 6-by Timber (Surfaced 4 Sides, S4S) NOMINAL SIZE (INCHES) a nominal 8x8 timber has a minimum finished size of 7.25" x 7.25"), most timbers over 7" are finished with 1/2" removed. While NIST Publication PS20 indicates that nominal 7" to 15" thick timbers should have 3/4" removed for a finished dimension (e.g.
Softwood lumber that has a thickness over 5" is called timber. North American Standard 4-by Lumber NOMINAL SIZE (INCHES) North American Standard 2-by Lumber NOMINAL SIZE (INCHES) North American Standard 1-by Lumber NOMINAL SIZE (INCHES) In the United States, softwood lumber is governed by the National Institute of Standards American Softwood Lumber Standard (PS 20). Softwood lumber is generally used for framing walls and floors.
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