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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.
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.
The HT mark means the lumber has been heat treated and has reached a critical temperature at the core to eradicate the "Pinewood Nematode" and its vectors. HT does not mean the lumber has been treated with a chemical preservative.
The courses provide a completion certificate. In order to be qualified to grade lumber in a lumber producing facility you will need additional on the job training. Thorough knowledge of the rules and ability to make the correct calls will need to be observed by an accredited grading agency.