Update: ALSC Issues Supplemental Ruling on SP Design Values
Originally published by: SBCA — January 12, 2012
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The Board of Review of the American Lumber Standards Committee (“ALSC”) today updated their approval with a supplement that provides an addendum to the 2x4 SP design values per the following table. These are the only design value changes that will be taking place effective on June 1, 2012.
A complete copy of the ALSC supplemental ruling is set out below.
Multiple discussions are taking place to set a foundation for the creation of a united approach or policy with respect to implementation of the above new design values. Please rest assured that key leadership in all industry segments will be involved in the final implementation policy using the experience and wisdom of our Southern Pine Design Value Forum group for the crafting process and final vetting.
To reiterate, SBCA believes this narrow ruling on the part of ALSC and the reasonable implementation date will allow for Southern Pine specifiers and users to effectively plan for a reasonable marketplace transition.
AMERICAN LUMBER STANDARD COMMITTEE BOARD OF REVIEW -- SUPPLEMENTAL RULING
In the Matter of the Submission of the Southern Pine Inspection Bureau for Approval of Supplement 9.
This is to clarify the January 11, 2011 ruling of the Board regarding the proposed design values for southern pine species. The ruling should have made clear that the approval was for No. 2 2x4 lumber and all lower grades of this size ( i.e. No. 3, Stud, Construction, Standard and Utility ). The recommended effective date for all of these grades is June 1, 2012. This approach is consistent with ASTM D-1990 and is mandated by the practical applications of these grades in the construction industry.
As the Board pointed out in its initial ruling, Section7.2 of D-1990 addresses limitations on the use of data from one grade for extrapolations to other grades. Given the full context of D-1990 and its practical implications, however, the Board has concluded that the principle of Section 7.4 does not apply to extrapolations from No. 2 2x4’s to lower grades in this size. For instance, Section X8.2.1 of D-1990 provides: “Property estimates for all grades below No.2 are estimated as the model predicted value at the grade minimum strength ratio (as listed in the grading rules).” Thus, the design values for grades lower than No. 2 are controlled by the No 2 2x4 cell and would not likely to be effected by the ongoing matrix testing of higher grades.
This interpretation is also mandated by the discontinuities of grade properties that would otherwise occur if the lower grades were maintained while No. 2 values were substantially reduced. This would lead to the anomalous result that Construction grade 2x4 would have higher values than No 2 2x4, for example. Because of different knot size allowances and other grading factors, Construction grade is, by definition, weaker than No. 2 2x4.
The Board regrets any confusion that this may have caused.