[GSBN] Straw bale at high altitudes
jeff at odiseanet.com
Fri Jul 11 14:05:16 CDT 2014
We build all the way up to 10,000 feet with lots of snowfall here in Colorado. I know its not California, but I know of a few bale homes built above 4,000 ft in that area. I am from the Sierra Foothills and have consulted on a few in that region. No problems I know of.
As for the sloped site, the bales on the main floor would sit on a framed deck on top of the foundation walls (the deck of the living space floor), so no need to make the foundation walls as thick as the bales. You can certainly step the foundation with the slope, but if you are going to use bales over those steps you will need to do something different in those locations. Some people frame a cripple wall to the interior of the foundation wall to create the platform needed for bales. This also allows them to insulate the interior of the concrete walls in a conventional way. Lots of little details to think of, but nothing too difficult.
There should be no headaches in your situation from using bales, other than from sucking straw during construction. ;-) We do homes on sloped sites all the time. Paying attention to the framing system and its interaction with the foundation is the key, which is the basis for your concern.
Jeff Ruppert, P.E.
ODISEA | Civil and Structural Engineering
Designing Your Vision
P.O. Box 1809
Paonia, CO 81428
On Jul 11, 2014, at 9:40 AM, Misha Rauchwerger <misha.rauchwerger at gmail.com> wrote:
> I have a client that wants to build a straw bale house at 4000 feet in the Sierra Foothills. They have been getting conflicting information about the wisdom of building with straw at that elevation. In particular there is the concern about the effects of moisture in the wetter months, and possible condensation inside the walls. They know about the need for big eaves, and permeable plasters, but have been swayed against the idea from a local green architect in town. Please direct me to any research, or anecdotal evidence to support straw bale construction under these conditions, or maybe there is valid concern. I have only built in the lower/dryer elevations on flatter sites.
> They also share these concerns:
> Their lot is sloped, so they would likely have to build a full walk-out basement on the lower level, and the living space on the upper level. This means that the full lower level is built of concrete (probably Faswall or Durisol); will they would have to build out the lower walls to match the width of the straw bales? How is this disparity in wall thicknesses usually resolved with the least cost/impact?
> - With a walk-out basement, is it possible/reasonable to do a stepped-foundation on the lower level to minimize the amount of concrete used? Or does the mixed use of concrete and post/beam and straw bale construction create unreasonable headaches in the building process?
> Thanks everyone for your comments,
> Misha Rauchwerger
> GSBN mailing list
> GSBN at sustainablesources.com
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