[Cob] Well it seemed like a good foundation...

[Peter Kaulback]

I built my cob oven in a 24 inch deep hole filled with gravel and 
crushed cinder block with the walls of my base made from old cinder 
blocks with the middle filled with more gravel and crushed cinder block 
and topped off with a 10 inch deep mix of sand and vermiculite. The land 
here is very high in clay, something like 90% and if it weren't for top 
soil we would grow bricks instead of crops :) So aside from using 
machinery to dig further, 24" was fine. I've dug 24" here before and 
when it rains the water stays in the dug hole and doesn't drain away.

Now the sand under my oven floor has shifted and fallen due to the 
drought this past year, there are still cracks in the field that are 2-3 
inches wide and several feet deep. As well there is one crack near my 
oven at the back of it which I suspect caused my problems.

Now I have been able to fill the new cave ins under my deck but I wonder 
what I could do in the future to prevent or lessen the impact of such 
natural occurrences?

Peter Kaulback