FAQ Category: Codes and Standards

Where single-number sound performance ratings, such as sound transmission class (STC), are available for individual components of an assembly, can these values be added together to determine an STC rating for a complete assembly?

As stated in Section 1.1 of ASTM E90, the scope of this standard is limited to building partitions such as walls, operable partitions, floor-ceiling assemblies, doors, windows, roofs, etc.  Although it is possible to use ASTM E90 to assess the sound transmission performance of individual components that would be used within an assembly, such use…

Are the provisions for wall studs and plates in the International Residential Code (IRC), Section R602 limited to the four major lumber species groups (i.e., Douglas fir-Larch, Hem-fir, Southern Pine and Spruce-pine-fir)?

No. In the southeastern U.S. where the ultimate design wind speeds are 130 mph or less (and in other areas where the ultimate design wind speeds are less than 140 mph), framing provisions for wall studs and plates and fastening schedules in IRC Section R602 are independent of the lumber species and assigned specific gravity;…

What is the difference between 2012 NDS 3.5 and 2012 IBC Table 1604.3 Footnote D for adjusting long-term deflection of wood members?

The provisions for calculating bending deflection in the National Design Specification (NDS®) for Wood Construction Section 3.5 increase the long-term deflection with a creep factor, Kcr.  The creep factor ranges from 1.5-2.0. These NDS design provisions relate specifically to estimating total deflection including the effects of long-term loading. The deflection limit for the D+L load combination only applies to the…

In a relatively active seismic zone, are heavy timber concentrically braced frames allowed? If so, what values (such as ‘R’) should be applied?

We didn’t find any discussion in any of the codes we’ve referenced. Nothing either allowed or disallowed. The prevalence of surviving historical structures suggest these may be viable. ********* The 2003 International Building Code (IBC) does not define seismic design coefficients for timber braced frames or three hinged arches. The only U.S. code source for…