WWPA grade-stamped structural-glued lumber is subjected to rigorous quality control and testing during production.
Test procedures are governed by WWPA's Glued Products Procedures & Quality Control C/QC 101.97. These procedures comply with criteria established by the ALSC'sGlued Lumber Policy. Under the WWPA procedures, samples are regularly selected from normal production, including samples for certification and hourly samples, for continuous quality control.
All structural-glued lumber products are subjected to durability-cycle or cyclic-delamination test. These tests are designed to simulate long-term, end-use conditions by subjecting the glued joints to changes in moisture content that cause wood to shrink or swell.
All structural-glued lumber products are also subjected to strength tests. Depending upon the product, specimens are tested under static-bending, tension or shear forces equal to or exceeding the published design values for solid-sawn lumber. Corrective actions are taken if any specimens fail strength or cyclic-delamination tests.
Full-size samples of finger-jointed (end-jointed) lumber stamped CERT EXT JNTS are tested in tension to verify joint strength. Tension testing applies a uniform stress across the joint so that joint strength will equal or exceed the published tensile-strength design values for the grade being produced.
Finger-jointed lumber stamped VERTICAL USE ONLY is subjected to bending tests. Because stud walls are often subjected to bending from short-term lateral forces such as wind, earthquakes and impact, tests are conducted to check the structural integrity of the glued joints under such conditions.
Following the durability-cycle test, specimens are subjected to fiber stress in bending forces to ensure joint strength equals or exceeds the published bending-strength design values for solid-sawn lumber of the same grade and species.
Both face- and edge-glued lumber are tested in shear to verify joint strength. Because glue lines are subjected to shear stresses in end-use applications, test specimens are selected and subjected to a durability cycle, then further tested to ensure the strength equals or exceeds the published horizontal-shear design value for the product.
WWPA's ongoing quality control program ensures the end user that WWPA grade-stamped glued products can be used interchangeably with solid-sawn lumber in full confidence.
WWPA: An Approved Quality Control Agency
Western Wood Products Association is approved by the American Lumber Standard Committee, Inc. to supervise solid-sawn, glued and machine stress-rated lumber production in accordance with the procedures of the U.S. Department of Commerce Voluntary Product Standard PS-20. WWPA also writes and publishes the Western Lumber Grading Rules, which are approved by the Board of Review of the ALSC according to the procedures of PS-20. WWPA's Glued Products Procedures & Quality Control C/QC 101.97 comply with the ALSC Glued Lumber Policy.
Only those products stamped with a WWPA grade-mark have been subjected to WWPA's rigorous quality control and inspection services.
Western Wood Products Association
1500 SW First Ave. Suite 870
Portland, Oregon 97201
Tel: 503-224-3930 | Fax: 503-224-3935 |