New design values for #2 and lower grade Southern Pine and Mixed Southern Pine 2×4’s will become effective on June 1, 2012. These reduced values, developed by the Southern Pine Inspection Bureau (SPIB), were approved by the American Lumber Standard Committee’s Board of Review in January. At the urging of NAHB and other industry stakeholders, an effective date of June 1 was provided to allow the industry some time to transition to the new design values while avoiding project delays and market disruptions.
As part of these efforts, the American Wood Council has developed addenda to the National Design Specification for Wood Construction, the Wood Frame Construction Manual, and the Span Tables for Joists and Rafters reflecting the new design values, and has also developed recommended amendments to prescriptive tables in the International Residential Code and International Building Code.
The new values were reduced by 25-30% and will primarily affect the design of roof trusses. Though the maximum allowable spans for 2×4 headers, joists and rafters will be shorter, they are not commonly used in those applications, and so will have minimal effects on most builders. In addition, 2×4 studs used in conventional construction are not affected by this change.
It is NAHB’s understanding that any such adoption would apply only to new construction. Projects already under construction or submitted to the building department prior to an adoption date should not be affected. However, builders are advised to consult with their local jurisdiction regarding any plans to adopt and enforce the new design values.
Going forward, SPIB is testing additional sizes and grades of Southern Pine. A submission to ALSC is expected in late summer or early fall, which may propose reductions to design values for larger sizes (e.g. 2×8 and 2×10) and higher grades (#1 and Select Structural). ALSC has also directed that the other major species (Douglas Fir, Hem-Fir and Spruce-Pine-Fir) should undergo sampling and testing to assure there are no changes to their current design values.
NAHB has created a special web page titled Information and Resources on Propposed Changes to Southern Pine Lumber Design Values that is dedicated to keeping our members updated on this issue. A “Frequently Asked Questions” document is in the process of being developed and will also be posted on that web page.
For additional information, email Gary Ehrlich at NAHB or call him at 800-368-5242 x8545.