Could spray foaming my crawlspace floor joists cause frost heave??

Chris74

I was just about to pull the trigger paying to have my floor joists sprayed with closed cell when I had a thought. My home was built in 1906 on a rock foundation. The foundation footing is about a foot deep. Code in my area calls for an 18 in footing on new construction because of our cold Ozark Mountain winters. Could shutting off all heat coming into my crawlspace from the heated area above cause my foundation to frost heave??? That may be a ridiculous thought, but could it happen???

Daniel Holzman

You say that your foundation was "built on a rock foundation". I guess I don't know what you mean. Are you saying that your foundation was built on rock (ledge)? Or are you saying that your foundation is fieldstone? Then you say your foundation is a foot deep. Does that mean the bottom of your foundation is one foot below grade?

My guess is that if you have not had frost heave since 1906, you are not likely to develop it just because you insulate the joists, since I doubt the amount of heat lost through the bottom of your floor would have been sufficient to prevent ground freezing.

shazapple

Older rock wall foundations are usually insulated from the outside to keep the wall warm, otherwise the freeze thaw will slowly destroy the wall. Good drainage helps with this too.

Windows on Wash

Insulating the stone from inside with keep it from drying out as readily.

A sacrificial parge coat and some good sealing of the exterior as well as proper moisture management should mitigate the risk.

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