ALSC Approves SPIB's Recommended SP Dense and Non-Dense Design Value Changes
Originally published by: SBCA — March 12, 2012
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In January, the Structural Building Components Association (SBCA) submitted a letter (to view, click on the first pdf link below) to the American Lumber Standards Committee (ALSC). In that letter, SBCA asked ALSC to clarify how it would rule with respect to design values for Southern Pine (SP) 2x4 No. 2 Dense versus 2x4 No. 2 Non-Dense.
ALSC provided its response in a letter today, March 12, 2012 (to view, click on the second pdf link below). In essence, the ALSC ruled to approve SPIB’s proposed design value reductions for SP 2x4 No. 2 Dense and SP 2x4 No. 2 Non-Dense (to view the SPIB’s recommendations, click on the third pdf link below). In the minutes from its March 9th meeting (to view, click the fourth pdf link below), ALSC provides the following reasoning:
“After consideration of all the information available to it, the Board approved the No.2 Dense 2 to 4 inches thick and 2 to 4 inches wide and No. 2 Non-Dense 2 to 4 inches thick and 2 to 4 inches wide southern pine design values as submitted by SPIB on February 10, 2012 with a recommended effective date of June 1, 2012.
In granting the above approval the Board noted the following:
In the previous submission by SPIB, which was approved by the Board on January 11, 2012, there was no differentiation between the design values for No.2 Dense 2 to 4 inches thick and 2 to 4 inches wide and No. 2 Non-Dense 2 to 4 inches thick and 2 to 4 inches wide southern pine lumber.
There has been a historic recognition by the Board and by other respected authorities that density of lumber contributes to its strength. The derivation of the dense and non-dense values in the SPIB submission followed or improved on procedures that have been used in previous submissions to the Board and in the derivation of the original in-grade values.
The Board also agrees that the use of the data from pieces actually tested provides a conservative value for No. 2 Dense and No. 2 Non-Dense 2 to 4 inches thick and 2 to 4 inches wide southern pine lumber based on “other technically sound criteria” as specified in Section 220.127.116.11 of P.S. 20.”
All of the latest information on the SP lumber design value issue can be found on SBCA's lumber web page.