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Frequently Asked Questions

    General Lumber FAQs

  • How are design values derived?
    • Design values provide guidance for designers to calculate the performance of a structural system and are assigned to six basic lumber properties. Design values for stiffness, as well as the major strength properties of bending, tension and compression parallel-to-grain, are based on data from destructive testing of samples of commercially-produced structural lumber. Design values for the minor strength properties of shear and compression perpendicular-to-grain are based on published clear-wood properties.

      Design values for structural lumber go through a rigorous approval process. As the rules-writing agency for Southern Pine lumber, the Southern Pine Inspection Bureau (SPIB) is responsible for developing and publishing design values for Southern Pine. All testing and data analysis must be completed in accordance with approved standards. Proposed design values are submitted to the American Lumber Standard Committee (ALSC). Design values are approved by the ALSC Board of Review following a careful review and recommendation from the U.S. Forest Products Laboratory.

      PDFDesign Values from 2014 Appendix A

  • How often are design values changed?
    • Design values have changed multiple times over the years based on available test data. The lumber industry conducts ongoing testing and invests millions of dollars to provide the most accurate and reliable design values for structural lumber. Comprehensive lumber testing is conducted as new technology becomes available or as warranted by changing resource data. The first significant lumber tests began in the 1920s, resulting in design values based on the strength of small clear-wood specimens. The last major change occurred in 1991 when design values for Southern Pine and other North American species were published based on In-Grade testing of full-size samples of commercially produced lumber.

      PDFDesign Values from Book 2014 Tables & Footnotes

  • Should I buy Southern Pine?
    • Yes. Southern Pine lumber remains one of the best construction products on the market today. It is the only lumber species that has been monitored annually since 1994, making it the most tested wood species in America. Southern Pine lumber continues to provide great value with its dependable strength and superior treatability against decay and termites. Southern Pine forests are some of the most productive and sustainable timberlands in the world, capturing large amounts of carbon from the air and storing it in lumber used every day. Southern Pine is grown and manufactured in the U.S. South, further improving local economies, reducing transportation costs and minimizing impacts on the environment.

  • Why isn't the species name on lumber marked with an SPIB grade-mark?
    • Under the provisions of US Department of Commerce Voluntary Product Standard PS-20, if the species is denoted by the agency's mark then the species name does not have to be duplicated. Any lumber marked as SPIB, with no additional species designation, is Southern Pine (also referred to as Southern Yellow Pine and often abbreviated as SYP). Lumber containing the minor species will be labeled as Mixed Southern Pine.