American Softwood Lumber Standard

American Softwood

Lumber Standard

The U.S. Department of Commerce’s American Softwood Lumber Standard PS 20 correlates lumber size to moisture content. Green and dry lumber are measured using separate size schedules to ensure both products will approximate the same size in service. Additionally, all bills and invoices must show actual net sizes of lumber.

Strength and stiffness values for Southern Pine lumber in current Southern Pine Inspection Bureau Grading Rules have been approved by the American Lumber Standard Committee’s Board of Review.

PS 20 provides for a National Grading Rule (NGR) for Dimension Lumber1 with simplified grade names and sizes to ensure uniformity, efficiency, and economy in the use of dimension lumber. The NGR was incorporated in the SPIB’s Standard Grading Rules for Southern Pine Lumber.

Lumber Standard

Dimension lumber sizes and grades are:

Structural Light Framing:

Light Framing:


Structural Joists & Planks:

1 NGR applies to dimension lumber and excludes items such as crossarms, factory and shop lumber, finish (selects), foundation lumber, industrial clears, ladder stock, laminating stock, railroad stock, rough lumber, scaffold planks, ship decking and plank stock, stadium plank, worked lumber, and special product rules for items such as radius edge decking, and prime and merchantable dimension.