We submitted our cabin plans and of course they got kicked back for corrections. Most of the corrections are minor. Most of them. One isn’t.

Short story: The foundation requires engineering.

Long story: Pima County, where we are building was the first county in the U.S. to adopt a straw bale building code amendment. It outlines the rules for building a house out of straw bales. If you follow the rules, you can get a permit and build a house and you don’t need an architect or an engineer.

To build a foundation according to this code, you have to construct a concrete footing that is as wide as the bales (and the bales have to be laid flat, so your foundation is two feet wide). Your bales have to rest flat on this foundation.

Our site is sloping, so we would have to either level the site and regrade it (difficult on our rocky terrain, not to mention destructive to the site) or build what is called a stepped footing. Which means we would have to build a stemwall up to six feet high where the ground is lowest. The average height of the wall would be three feet, and if the foundation is two feet wide, that’s six square feet of concrete per foot of foundation. Our foundation is about 96 linear feet, so we would need 576 cubic feet of solid concrete, or about 22 yards. Then we would need another 8 yards or so for the floor. So that’s about 30 yards of concrete total. For a cabin. If the site were level and it were a stick-framed house, the slab and foundation would require about 10 yards.

All that concrete would have to be trucked to our rather isolated location, pumped uphill to the site, and finished by professionals. Very expensive and not at all “green”.

The alternative is to construct a pier foundation. Basically put the house on stilts, with the stilts supported by small concrete pads. The floor structure would be made of small dimension wood. All of the components may be easily delivered on the back of a pickup truck or small flatbed truck, and assembeld by hand without heavy equipment. Total concrete use for 21 generously oversized footings: maybe four yards?

Unfortunately there is no prescriptive code for this sort of foundation, so we need engineering.

The good news is we found a local architect who is willing to help us out. I will get to do the drawings to save some money, and the county agreed to accept his stamp on my plans.

So progress is being made. I like the architect we are working with and the changes seem straightforward. We shall see how quickly things go.

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