Cob: frost free shallow foundation

[Theodore L. Stacy]

Shallow frost foundations are the subject of a HUD publication.  The site
url is: http://www.cs.arizona.edu/people/jcropper/desguide.html  Shallow
means shallow.  The Swedes use them for most houses. In general they are
slabs with thickened edges.  The slab is insulated down about 18" (slab
thickness at edge) and out about two feet.  The idea is to keep the earth
heat under the slab and therefore  to keep the soil from freezing.  They
work and eliminate the need to excavate to 4' or so as in the usual
construction.  I'd use a little more insulation than the minimum because it
will help with the floor temperature control, especially if you use radiant
heat (the best).  Check with your building department and get them to buy
into the idea once you have the info and if you want to go that route.  If
you are planning a basement, then you cannot do a shallow design because the
freeze pressure would be too great.

I do not believe Wright used this method.  He used rubble foundations for
some work, and those are entirely different. TS