[Cob] foundation

[Anna Young]

Hey, those names sound familiar. If you are the Saltspring guys we have met 
at the ECO village for a cobbing session already. We are building a 
cob/strawbale on the edge of Victoria, BC, with codes etc. I think your 
foundation depends a lot on where you are and whether you have building 
inspectors involved. Ours turned pale when we mentioned a rubble trench 
right under the wall....

We are in an earthquake zone and building close (6m) to the top of a 
30-45deg slope close to the water. We are overbuilding as a result, in 
preparation for the big earthquake and tsunami that will be here one day. We 
are doing a poured reinforced cement bond beam with 4" poured reinforced 
cement stemwall. The stemwall height is variable depending on the height of 
the finish ground level. Wet-mortared stone/urbanite (for the earthquake 
zone) will hide the stemwall and give the width needed for a cob/strawbale 
foundation.

Yes, you could reuse the form wood, though for somewhere that will not mind 
having concrete dust sifting onto it from the wood. Many salvage yards will 
have secondhand ply which has already been used for forms once, though keep 
a skilsaw with a beater blade for cutting through it.

Big debate here at the moment about the exact height of the stemwall. I want 
to stop it a few inches below the start of the cob, and have a final layer 
of wet-mortared stone/urbanite over, to prevent moisture being wicked up 
into the cob. Architect plans and husband feel it's better to have the 
stemwall right up to the start of the cob, and separate the two with 
heavy-duty waterproofing like roofing paper or roll roofing. My concern is 
that this will fail eventually and then we will have wicking. Roofing paper 
gets fragile after a couple of years underground. Plus I hate the idea of 
having asphalt in the wall or painted on the outside of the stemwall as a 
waterproof layer. Input/comments welcome!

Anna