|
More Challenges Ahead on ICC Wall Bracing Requirements
During the recently completed International Code Council's (ICC) code amendment cycle, building officials voted in improvements to the wall bracing requirements for houses to resist wind and seismic loads, which have been one of the most contested items in the code, but some interests are already at work on other proposals involving this issue that could be detrimental to home builders.
Among the approved changes to Section R602.10 and R602.11 on wall bracing made to the ICC’s 2007 supplement to its family of model codes:
- An extensive non-technical rewrite of the section now groups together provisions on braced wall line amounts, spacing, methods and braced wall support requirements. Previously, they were scattered throughout the sections. The rewrite also introduces new figures to illustrate existing code language.
- As proposed by NAHB, requirements for the continuous sheathing method have been clarified. Among other improvements, this has removed the onerous requirement to fully sheathe interior braced wall lines with plywood in order to use the method. In addition, builders in areas with a low risk of earthquakes or hurricanes can now combine the continuous sheathing method with other approved braced wall methods within a single story or on different stories of a house.
- Use of the portal frames developed by APA — The Engineered Wood Association has been expanded. This wall bracing method, which allows constructing braced wall segments with narrow 16-inch or 24-inch piers connected by a header, can now be used at door and window openings around the house, not just at the garage door. The new provisions extend use of the portal frames to upper stories of the house and allow their use in high seismic areas as well.
The ICC’s Ad-Hoc Committee on Wall Bracing and the Building Seismic Safety Council's (BSSC) IRC Sheathing Task Group continue to pursue major technical changes and clarifications to the wall bracing requirements.
Much of this effort has been devoted to revising the required wall bracing amounts in Table R602.10.1 to reflect new shear wall test data, to split the requirements for wind and seismic loading and to reflect the concerns of the seismic community with the behavior of houses in earthquakes and particularly with the performance of drywall finishes.
In addition, there is pressure from some product representatives and the seismic community to introduce more engineering-based provisions — including increased foundation and footing requirements — particularly for interior braced walls, as well as uplift hold-down requirements and limits on cripple wall construction.
These efforts could lead to code proposals for the 2007 to 2008 and subsequent code development cycles that would substantially increase the wall bracing amounts and other requirements. These provisions could potentially limit builder and designer flexibility and substantially increase the cost of building a home.
NAHB is represented on the ICC Ad-Hoc Committee and in the BSSC Task Group and NAHB staff members continue to closely monitor the issues related to this section and to strongly advocate provisions that are cost-effective and reflect the excellent performance of conventional wood-framed construction under normal circumstances and in wind and seismic events.
For more information, e-mail Gary Ehrlich at NAHB, or call him at 800-368-5242 x8545.
|
