Is there an expandable building material that can fill large voids in walls to prevent mice from entering?
Answers:
There is expanding insulation that you can spray into it, but I would not use anything that a mouse can chew his way thru. I would pack the hole with steel wool instead, and then seal it with caulking or drywall mud. Steel wool will stop them every time.
Other answers:
Bob vila used expandable foam insulation in one of his shows. put a line of it btw studs and it expanded to fill the whole region (even had to cut some off. Than might help.
Bob vila used expandable foam insulation in one of his shows. put a line of it btw studs and it expanded to fill the whole region (even had to cut some off. Than might help.
I would caution you about the expanding foam. It can be very effective but it also can put a huge amount of force on things like dry wall if it is sprayed inside the wall in too large a quantity at one time. It can cause the wall to bulge.
foam spray in a can
Depending on how big this project is....there's a foam insulation you can drill hole in wall and squirt it in.