[Cob] psi testing

[Henry Raduazo]

	I have a room that is 10 ft. wide and 36 ft. long. Two 8 inch thick  
cob walls are supporting a 12 foot wide living roof. (The US standard  
for such a roof is an assumption of 50 pounds per square foot.)  Take  
a 10 ft. X 12 ft. segment of the roof structure 10' X 12' X 50 lb. :  
You have a calculated weight of 6000 pounds for 120 square foot of  
roof. Divide this by 16 inches (the thickness of the two supporting  
walls) x 120 inches (the number of inches in a 10 ft. segment of  
wall) i.e. 1920 square inches in two 10 foot wall segments. You will  
get a load of 3.125 pounds per square inch. Why would you need a load  
bearing strength of 350 psi (pounds per square inch)? Or, What sort  
of structure would require a strength of 350 psi.?
	For my structure 350 psi. would give me an 11200% safety margin.  
Does that sound right to you? I don't usually bother with such  
calculations because I assume some future owner will do something  
really stupid like running a lawn sprinkler against the wall. Then of  
course all bets are off.
	Is this a code requirement for earth walls? It seems rather  
arbitrary to apply something like this to cob unless you are pushing  
limits which should not be pushed.



Ed



On Sep 17, 2010, at 11:05 PM, Janet Standeford wrote:

>  Hi all,
> I turned in the original cylinder of cob to be tested for psi. I  
> needed 350 for a load bearing wall but my walls are not load  
> bearing and the cob tested at 360!
>
> I'll see whether or not that is good enough. If not, I'll go with  
> the other five in cube form.
>
> -- 
> Janet Standeford OR
> www.buildingnaturally.info (Owned by you)
> A resource for healthy homes.
>
>
>
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