NAHB Proposes Code Changes on Wind Effects, Foundation Walls
Ranging from minor administrative changes to requests to change construction methods that otherwise could cost home builders more money and take a toll on housing affordability, NAHB has submitted 65 proposals to the International Code Council (ICC) for discussion during the upcoming 18-month 2006 cycle of code revisions.
Among the proposals submitted by NAHB:
- New sections on topographic wind effects. Advocates for the wind engineering community have been pushing in recent years to add provisions to the International Residential Code that would mandate consideration of topographic wind effects.
To ensure that overly conservative engineering estimates of so-called “wind speed-up” are not applied arbitrarily to every home on a ridge, hill or mountainside, NAHB has proposed limiting these design provisions to areas where local historical data show that structural damage from wind speed-up has occurred.
With this proposal, NAHB is trying to help members avoid the needless expense of structural engineering consultation on wind analysis and design in areas where exceptionally severe winds are not a problem. “Reports of structural failures of homes due to wind speed-up have been extremely small and limited to areas were there are dramatic changes in the ground topography,” according to the NAHB proposal. Delineating those areas where it might pose a problem represents “a balanced approach,” NAHB said.
- Removing recent changes describing lateral support of foundation walls. ICC provisions for laterally supporting basement walls that were originally taken from the CABO model code were changed in the 2003 cycle after proponents convinced code council members that the CABO provisions had resulted in foundation failures.
However, “no detailed data to substantiate those failures was provided,” the NAHB proposal says, and the provision was voted in late at night “with a very small representation of the voting membership present.” Under NAHB’s proposal, the code would return to the earlier, successful CABO-based foundation wall, which also is easier to comply with and more affordable.
- Refine continuously-sheathed braced wall panel requirements. NAHB is seeking to drop current ICC requirements for all walls to be fully sheathed with wood structural panels because they are inconsistent with IRC 2000 language and with the technical basis for IRC bracing provisions.
Wall-bracing requirements are confusing to many builders, NAHB code experts note, and the new language is meant to clarify what needs to be done.
Joining more than 2,000 other proposals from various industry advocates, suppliers, local code officials and individual home builders, the NAHB proposals will be debated by ICC members in the fall. Members of the NAHB Construction Codes and Standards Committee will review all of the proposals after they are compiled by the ICC in July.
For more information, e-mail Calli Schmidt at NAHB, or call her at 800-368-5242 x8132.