compressive capacity

[goshawk at gnat.net]

I receceived the following message:


Dear Pat
It's good to find out what your soil's compressive capacity is, because a 22
ft. dome is large and will be heavy on the bearing soil. You may have to make
a wider (and deeper) footing, including reinforcing steel if your soil will
not allow the weight you will put on it, because it may sink and settle. It's
good for you to know if your soil's compressive strength is above 2000 lbs
per sq. ft. (psf). That's when soil engineering/tests comes in.


(end of message received)

Now cob building are quite heavy. To be honest I don't think I can 
afford a soil engineering test. My soil  is quite sandy. I have dug 
as far as 4 feet and it's still sand. 
I've seen it hold big dump trucks, does that count?
I plan on going to our local county office of one kind or another and 
ask what the general soil compressive strength is around here.
Any bets if my earth dome will sink?
Any thoughts or words of advice.
the soil is very consistant in make up. 
I plan on using a 2 foot footer with 15 inch walls.


(P.S  thanks for all the help on the septic line, it's looking good!)
Pat in Mauk,


"Any sufficiently advanced technology is indistinguishable from magic" Arther C Clark