# Spray foam between sill plate and foundation?



## jimcrook (Oct 21, 2014)

My recently-purchased 1949 one-story ranch has a crawl space with untreated sill plate resting on top of a somewhat wavy (in places) foundation wall. There's tar paper or something like that between the wood and concrete. 

Because the top of the foundation isn't perfectly flat, there are large areas with about a 1/2" to 3/4" gap between the sill and the concrete. The original builders shimmed it in various locations. 

Mice infested the crawl space and batt floor insulation in the past, and I removed it over the summer (nasty). I'm doing everything possible to exclude rodents and was thinking that I should stuff some copper mesh into the gaps between the sill plate and the foundation, and then squirt some canned spray foam over that (between wood and tar paper). 

Is there any reason I shouldn't do that? 

My only concern is that this might somehow lead to rot issues since I live in the maritime Pacific Northwest, but if spray foam does not wick moisture then I should be good, right? The exterior vinyl siding is in good condition and does prevent our constant rain from getting the sill and nearby framing wet.

Thanks!


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## Windows on Wash (Aug 30, 2011)

The tar paper is serving as the capillary break so it should be fine. 

Make sure the water can still drain out if need be and do it from the inside surface.


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