The American Softwood Lumber Standard PS 20, of the U.S. Department of Commerce, relates lumber size to moisture content. Separate size schedules for green and dry lumber assure that both products will approximate the same size in service. All bills and invoices are required to show actual net sizes of lumber. Strength and stiffness values for Southern Pine products in current SPIB Grading Rules have been approved by the Board of Review of the American Lumber Standard Committee. PS 20 provides for a National Grading Rule (NGR) for Dimension Lumber1 with simplified grade names and sizes to assure uniformity, efficiency and economy in the use of dimension lumber. The NGR was incorporated in the SPIB Standard Grading Rules for Southern Pine Lumber, published by the Southern Pine Inspection Bureau.
Dimension lumber sizes and grades are:

The American Softwood Lumber Standard PS 20, of the U.S. Department of Commerce, relates lumber size to moisture content. Separate size schedules for green and dry lumber assure that both products will approximate the same size in service. All bills and invoices are required to show actual net sizes of lumber. Strength and stiffness values for Southern Pine products in current SPIB Grading Rules have been approved by the Board of Review of the American Lumber Standard Committee. PS 20 provides for a National Grading Rule (NGR) for Dimension Lumber1 with simplified grade names and sizes to assure uniformity, efficiency and economy in the use of dimension lumber. The NGR was incorporated in the SPIB Standard Grading Rules for Southern Pine Lumber, published by the Southern Pine Inspection Bureau.
Dimension lumber sizes and grades are: