The Southern Pine Inspection Bureau (SPIB) has issued Supplement No.9 to the 2002 Standard Grading Rules for Southern Pine Lumber providing new design values effective June 1, 2012. The only design values that will change on June 1 apply to visually graded Southern Pine and Mixed Southern Pine sized 2” to 4” wide and 2” to 4” thick (2x2s through 4x4s) in No.2 and lower grades (No.2, No.3, Stud, Construction, Standard and Utility). This also includes new design values for No.2 Dense and No.2 NonDense Southern Pine. Design values for all other grades and sizes of visually graded Southern Pine remain the same, pending results of testing scheduled for completion later this year.
The last major change for visually graded dimension lumber 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. Since 1994, SPIB has conducted an annual resource monitoring program developed in collaboration with the U.S. Forest Products Laboratory (FPL). SPIB is the first rules-writing agency to publish new design values. Rules-writing agencies responsible for other species are in different stages for evaluating design values.
Design values for structural lumber undergo a rigorous approval process. SPIB partnered with Timber Products Inspection to sample No.2 2×4 test specimens according to a plan approved by the American Lumber Standard Committee (ALSC) Board of Review. SPIB and Timber Products conducted destructive tests in bending and tension, plus gathered stiffness and property data, all in accordance with ASTM International standards. Throughout the process, technical review was performed by FPL. The ALSC Board of Review approved the new design values early in 2012 with a recommended effective date of June 1, 2012.
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