From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
Date: Thu, 3 May 2001 23:39:39 -0400
I would be very cautious about adopting or using the 1- and 2-Family Dwelling
Code in earthquake (Zones 2, 3 and 4) country. It should be remembered that
the Dwelling Code is the offspring of the CABO 1- and 2-Family Dwelling Code
and although CABO is the organization of model code organizations, very few
seismic requirements are in that code.
While SEAOC has been instrumental in developing earthquake design
requirements, their approach (and rightfully so) has been that they are
developing for California and what other states want to do is up to the other
states. Those of us in Zone 2 land have been remiss in not being active in
the code development area and have defaulted to others to specify what
should be required in Zone 2, however wrong it might be. The UBC governs
design in California. Only BOCA and SBCCI land (and other isolated
jurisdictions outside of California) have adopted the CABO code. BOCA and
SBCCI land think that they don't have earthquakes, so earthquake requirements
of the Dwelling Code mean little to them and the less said about earthquakes,
Unfortunately, ICBO took the last CABO dwelling code (1995?), reprinted it
incorporating the 1996 & 1997 amendments to the CABO code, and renamed it
the 1999 International One- and Two-Family Dwelling Code. It still has very
little seismic requirements, and requires that in Zone 4, residences be
designed for the UBC/IBC requirements. In fact, the seismic zone maps in the
1999 code are so distorted that it is difficult to determine anywhere near
where Zone 3 ends and Zone 4 begins. However, having the date of 1999, and
the title, "International One- and Two-Family Dwelling Code" gives it aura of
authority in the seismic area that it doesn't deserve.
Hope this helps.
A. Roger Turk, P.E.(Structural)
Scott Haan wrote:
. > Anyone else who has adopted the IBC in high wind-seismic area:
. > IBC 1704.1 exempts one and two family structures governed by the IRC from
. > the general special inspection requirements. IBC 1705.1 exempts R-3
. > occupancies not exceeding 2 stories and without structural irregularities
. > from a "Quality Assurance Plan" for seismic resistance.
. > Special inspections for seismic resistance are covered in IBC 1707. I do
. > not see where this section exempts one and two family construction from
. > special inspection for seismic resistance. It would appear special
. > inspection is required for "seismic resistance" although a "quality
. > assurance plan" is not required. This special inspection included 1707
. > includes periodic inspection of wood building lateral force resisting
. > system connections and members.
. > How are other jurisdictions enforcing special inspection for residential
. > construction and interpreting IBC 1707 "special inspections for seismic
. > resistance" for residential construction?
. > Thanks,
. > Scott M Haan P.E.
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