[Cob] Cob structures and "basements" or sunken floors

[Shannon C. Dealy]

On Sat, 4 Mar 2006, David Boyer wrote:

> Fellow Cobians and wannabes,
>
>   We have recently been informed by a (Linn) County, Oregon building 
> inspector that we can build all the cob cottages we want without a 
> building permit providing they are separated by at least 3 feet; that 
> the highest point of the roof is not more than 10 feet above ground and 
> that they are not larger than 200 square feet. (We want to get this in 
> writing on County stationary/correspondence before we begin 
> construction)

What you are describing is roughly the current definition for unpermitted 
structures (such as accessory buildings) given in the international 
building code (which Oregon has adopted at least in part).  Unfortunately, 
my recollection is that the 10 feet given in the code is not "above 
ground", but rather from it's lowest to highest point.  There is no 
provision allowing these to be used as a residential structure, and any 
plumbing and/or wiring must still be permitted and inspected.  I'm not 
saying you can't live in it, that's your call, however, be aware that 
legally it won't be a house.  I would recommend getting a copy of the 
current Oregon codes and reading them rather than relying on anything 
verbal from the county (you're probably safe on anything they give you in 
writing, but even that is no guarantee), many libraries carry or can get 
copies of local building codes.

> A 200 square ft cob structure would fit our needs if it had 2 stories 
> (400 sq. ft.). A way to get around the 10 foot roof height limit for a 2 
> story structure would be to have the bottom floor be below ground level 
> at least 2 feet (3 feet would be better).
>  No cob construction literature I have read covers the subject matter of 
> below ground living space. No Cob workshop I have seen offered has this 
> topic on the agenda.
>    Why?

Because buried walls must be able to handle the lateral loads of all the 
earth surrounding the building, as well as all the moisture wicking 
through the ground, and any possible running/standing water that may get 
channeled by the surrounding earth into direct contact with the walls. 
Simply put, cob is not up to this.  I don't mean this can't be done, 
however, to do it safely would not be easy.

Shannon C. Dealy      |               DeaTech Research Inc.
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