A Transparent Review of SPIB's Supplement 13 & Appendix A

Originally published by: SBCAMay 28, 2013

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The following article summarizes the recent changes made to Appendix A of the Southern Pine Inspection Bureau's (SPIB) Supplement 13 to the 2002 Standard Grading Rules for Southern Pine Lumber. Supplement 13 contains the Southern Pine (SP) design values effective June 1, 2013.

Below is the language of Appendix A from SPIB’s 2002 Standard Grading Rules for Southern Pine Lumber follows, with the portion prior to the “Mixed Southern Pine” section being the predecessor to the proposed language in Supplement 13:


Leading up to the American Lumber Standards Committee (ALSC) Board of Review meeting held on January 30, 2013, SPIB provided a draft Supplement 13 that included the amended Appendix A that follows (key elements of it are highlighted):

At the January 30, 2013 ALSC Board of Review meeting, the Structural Building Components Association (SBCA) raised objections to the amended language in Appendix A highlighted above. After the objections were discussed, a motion was made by Dr. Don Bender, P.E. of Washington State University, representing consumers on the ALSC, to amend SPIB's recommended Appendix A  by removing the sentence highlighted in blue above. The ALSC Board of Review adopted that motion, and then approved SPIB's Supplement 13.  

To summarize, the operative words of Supplement No. 13, Appendix A, opposed by SBCA but approved by ALSC to go into effect June 1, 2013, are the following:

"Wood is a natural product subject to variations in geography, climate, specific site characteristics, silvacultural practices, and harvesting decisions. Its’ strength properties are not only anisotropic (vary by principal axis) but also can vary with proximity to the center of the tree. These characteristics complicate the assignment of individual pieces into design value groups based on the visual appearance…..

This value is then used to establish the design value. Each piece or lot of visually graded lumber is not mechanically tested to verify strength properties. Since the stress ratings are representative of the entire producing region, lots from a specific location may have physical properties at the extremes of the property range or statistical distribution representing that range of strength values."

Again, the language removed from the final version stated:

"Designers of wood structures are cautioned to take into consideration the variability of wood within a species and grade grouping."

The resulting Supplement No. 13 can be viewed by clicking on the pdf link below.  The cover page, Appendix A and the design values footnotes have been copied and inserted below for quick reference.

The final language contained in Appendix A:

Often unread, the highlighted portions of the footnotes provide important design value insight:


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