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One and Two Family Dwelling: IBC 1707 "

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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, 
the better.

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)
Tucson, Arizona

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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