The current editions of the International Building Code (IBC) and the International Residential Code (IRC) include span tables to be used in the design of wood joists. The design criteria is established by Department of Commerce standard DOC PS 20-5, American Softwood Lumber Standard, which is also referenced in both the IBC and IRC. This standard identifies the American Lumber Standard Committee (ALSC) who administers an accreditation program for the grademarking of lumber produced under the system.
On January 11, 2012 the ALSC Board of Review certified reduced design values for 2x4 lumber sizes of Southern Pine of grades #2 or lower, effective June 1, 2012. In making this reduction, they stated the following: ‘The values represent approximately a 25-30% reduction…All design professionals are advised in the strongest terms by the Board to evaluate this information in formulating their designs in the interim period.’
As a result of this action taken by the ALSC, the ICC Board is directing the ICC membership to the American Wood Council website where the effect of those changed design values on the span tables contained in the IBC and IRC may be found.
The investigation of the adequacy of design values for other Southern Pine lumber sizes and grades is on-going.