Spray foam on stone walls (not basement)
I have a small 150 year old stone house. We’re in Ontario, Canada so lots of freezing winter conditions. The walls are 22″ thick and sit right on the bedrock, about 2ft down. The floor was rotten – logs split and laid in the dirt with the flat side up, then covered with planking. We dug all the dirt out down to the bedrock, back-filled with packed gravel, insulated -perimeter too- and topped with a 4″ heated concrete slab. We have framed with 2x4s about an inch out from the stone wall in preparation for closed-cell spray foam.
Will spraying the foam directly onto the interior of the stone wall cause damage from trapping moisture?
There seems to be some with strong opinions (usually historical purist-type people who believe it it wasn’t used when the house was built it shouldn’t be used now) that say the walls will be destroyed in short order because moisture migrating into the walls will be trapped by the foam, then freeze.
I understand there could be something to this, but the wall is not a one-way street. So moisture won’t be able to dry to the interior anymore…why couldn’t it dry to the exterior?
Thoughts on this? And if you have direct knowledge of damage caused be the application of spray foam to a stone wall, I want to hear about it!