[Cob] foundation question

[Shannon Dealy]

On Mon, 25 Aug 2008, Bob Smolen wrote:

[snip]
> If the foundation wall extends below the frost line, wont the earth above
> the frost line still shift so that the foundation wall imbedded in earth
> below the line is a rigid force against which the heave will work against

It is important to remember that your foundation is surrounded by earth 
both inside and out, so when the wet ground freezes and expands, it is not 
just pushing against the side of your foundation, it is pushing against 
all the earth on the other side of your foundation.  Basically, when the 
expansion occurs, if the soil on both sides of the foundation is well 
compacted, there is really no where for the forces to go other than up
since that is by far the path of least resistance, so if your foundation 
extends below the frost line, the forces are moving up along side your 
foundation, but if your foundation is not below the frost line, then the 
forces are pushing up on the bottom of your foundation as well, creating 
the frost heave effect.  There will undoubtedly be some minor lateral 
movement in the initial years after construction while the soil settles in 
and compacts down as well, but this movement would normally be 
insignificant.

Shannon C. Dealy      |               DeaTech Research Inc.
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