Foam is soft
Foam is quick to spray, but it is soft, so we don’t use it. We close every gap with galvanized steel mesh, putty and concrete.
Small gaps matter
The CDC notes that a mouse can fit through a hole the width of a pencil, about 1/4 inch. That is why we seal the small gaps too, not only the big ones.
Inside and outside
We seal openings inside the attic, crawl space and garage, and the ones outside: vents, eaves and roof gaps. See sealing outside openings.
Then we check
Traps catch the rodents already inside. We come back at least two weeks after the job to check them. See rodent proofing.