Understanding WWPA Grade Stamps

Grade Stamps
Western Wood Products Association is one of the largest associations of lumber manufacturers in the United States, representing sawmills in the 12 western states and Alaska. The Association's Quality Services Division supervises lumber grading by maintaining a highly competent staff of lumber inspectors who regularly check the quality of mill production, including visual grade requirements of glued products and machine stress-rated lumber.

The Association's Grading Rules for Western Lumber establishes standards of size and levels of quality in conformance with the American Softwood Lumber Standard PS 20. The Association is certified as a rules writing and inspection agency by the Board of Review, American Lumber Standard Committee. The Association is approved to provide mill supervisory services under its rules and the rules of the West Coast Lumber Inspection Bureau, the Redwood Inspection Service, the National Lumber Grades Authority for Canadian Lumber and the NGR portion of the Southern Pine Inspection Bureau Rules. In addition, WWPA is approved to supervise finger-jointed and machine stress-rated lumber.

Interpreting Grade Marks

WWPA uses a set of marks to identify lumber graded under its supervision. The grade marks are stamped on the lumber and appear near the ends of the product:


Most grade stamps, except those for rough lumber or heavy timbers, contain 5 basic elements:

WWPA certification mark Certification Mark certifies Association Quality standards and is a registered trademark.

Mill identification Mill identification Firm name, brand, or assigned mill number. WWPA can be contacted to identify an individual mill whenever necessary.

Grade designation Grade Designation Grade name, number or abbreviation.

Species identification Species mark Indicates species by individual species or species combination.

Condition of seasoning Seasoning mark Indicates condition of seasoning at time of surfacing:

    MC-15, KD-15

    15% maximum moisture content

    S-DRY, KD

    19% maximum moisture content


    over 19% moisture content (unseasoned)

Lumber carrying the WWPA grade stamp will meet or exceed the performance and aesthetic standards set for each grade. For additional information about lumber grades, sizes and specifications, go to WWPA's exclusive Online Technical Guide or check out the WWPA publications list.


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