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RE: builders win big in first code hearing round

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Dan,

This is a proposal for the IRC.  There have been several attempts over
the last several code cycles to bring the wind-speed up provisions from
ASCE 7 into the IRC.  These previous proposals have failed for a number
of reasons, including failing to define key terms required for
enforcement and failure to provide an appropriate prescriptive method
for determining the speed-up effect (since the IRC is supposed to be a
prescriptive code, after all).

This year there were two competing proposals.  There was one proposal
(from another WA engineer actually) which provided a simple prescriptive
method, but which still failed to define some of the key terms from ASCE
7 and left some key language out of the ASCE 7 triggers.  Also, it
didn't provide any guidance to building officials (or designers for that
matter) where you'd *really* need to apply the provisions.

Our proposal left out the prescriptive method but included all the key
ASCE 7 definitions and terminology (notably, the "abrupt change in
topology").  We also limited the application to areas where topology is
really a problem by requiring jurisdictions to indicate in the IRC's
proscribed design criteria table if wind speed up needs to be
considered--like in Washington state, where I know you folks have houses
perched on the top of high escarpments where it's pretty clear you're
going to get a topographic effect. (I contrast this with an experienced
fellow engineer living in suburban MD, exposure B, with lots of trees
around, but on a hill that just barely qualifies under the ASCE 7
triggers.  He doesn't think his house is underdesigned if the
topographic effect isn't considered.)

I should note we actually tried at the hearings to incorporate the best
parts of both proposals--combining our more-reflective-of-ASCE-7
language with the competing proposal's prescriptive table.  The
modification was ruled out of order and our proposal passed as is.  I'm
expecting the other proponent will submit a public comment asking for
his tables to be added to our approved charging language.

Hope this clarifies things a bit (or have I raised about five other
issues?)

Gary

Gary J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
1201 15th Street, NW, Washington, DC 20005
ph: 202-266-8545  or 800-368-5242 x8545
fax: 202-266-8369
gehrlich(--nospam--at)nahb.com

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