Lumber Size Categories

This blog is the second in a series of articles intended to provide information about softwood lumber, including grade-marking, design properties, testing, and continued monitoring of the lumber resource.

American Softwood Lumber Standard
There are several ways to classify lumber which are spelled out in the American Softwood Lumber Standard – Voluntary Product Standard PS 20-15. This standard is published by the National Institute of Standards and Technology (NIST) which is under the US Department of Commerce. The most recent version of PS 20 was approved and published in 2015. This American Softwood Lumber Standard was developed by the American Lumber Standard Committee (ALSC). From the abstract of PS 20: “This standard established standard sizes and requirements for development and coordination of the lumber grades of the various species, the assignment of design values when called for, and the preparation of grading rules applicable to each species. … It establishes principal trade classifications and lumber sizes for yard, structural, factory and shop use and provides for the classification, measurement, grade marking of rough and dressed sizes of lumber items.”

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