[GSBN] Zone D Load Bearing

martin hammer mfhammer at pacbell.net
Thu Jun 23 05:01:04 CDT 2016

Hi Mark. 

Load-bearing one-story SB dwellings are allowed prescriptively in Appendix S
in the International Residential Code (IRC) in seismic design categories D0,
D1, D2. It looks to me that about 20% of Idaho is in one of the D

As far as I know Idaho has not adopted Appendix S as its ³strawbale code²
and it has no other strawbale code I¹m aware of. However, Appendix S could
be proposed to the local building official as the code for the project(s).

I think you have Appendix S, but it is also available with its commentary on
the website of the California Straw Building Association (CASBA) at

See Section AS106 and especially AS106.12 and AS106.13 for structural
strawbale walls.

It might be helpful to inform the building official that Appendix S has been
adopted in Maryland, New Jersey, California (effective 1.1.17), City of
Denver and Boulder County in Colorado, and is on course for adoption in New

If you want to engineer the homes (if your design(s) fall outside the
prescriptive limits of Appendix S) showing the building official
load-bearing SB is allowed allowed in the D categories in the IRC might lend

You could also use a conventional lateral-force-resisting system that is in
the Idaho building code (as opposed to strawbale shear walls) but still with
load-bearing SB walls. However, the additional weight of the SB walls must
be accounted for in whatever lateral system is used.

Feel free to call if you need more help.


Martin Hammer, Architect
1348 Hopkins St.
Berkeley, CA  94702
510-525-0525 (office)
510-684-4488 (cell)

On 6/22/16, 6:41 PM, "Big M Construction" <bigmconst at gmail.com> wrote:

> Greetings all,
> I have been contacted to possibly build nine straw bale homes in Idaho. They
> are on a tight budget and I would like to build these as load bearing single
> story homes. Any thoughts out there on Zone D seismic and being able to do
> this. I have done load bearing in Zone C but not D.
> Thanks for your valuable thoughts,
> Mark
> Mark Jensen
> Owner
> Big M Construction
> PO Box 1596
> Bozeman, MT 59771
> (406)599-4220 (Cell)
> (815) 305-1393 (Fax)
> bigmconst at gmail.com
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