This is a sort of follow up to Locating the source of a fiber glass smell, or finding wet, dirty fiberglass insulation? (in that I believe the mice from here are managing to climb up the interior walls and nest in the first floor ceiling).

I set up some cameras in the garage, and have caught many instances of mice moving around. Here is one and a second [seems like I cannot upload them directly here since they are videos.)

I have attached a picture below with locations they are traversing. The red arrows indicate places they are entering/exiting the actual house from. The blue arrows indicate areas they are traversing (there is a significant space between the steel beam and the brick "wall", so they can pass right behind it).

The bundle of wires at right will (mostly) be removed - they are for an old lighting system that the former owner installed which no longer exists. A single twisted pair of wires will remain, for the dogs invisible fence.

Do you have any suggestions what I can fill this area with to prevent these mouse escapades? I would like to use spray foam, but I understand they'll chew through it. I would really like a "spray cement."

enter image description here

  • 2
    a sandwich of spray foam and steel wool should plug things up.
    – dandavis
    Commented Mar 28, 2022 at 12:34
  • @dandavis I like it - just to be clear, the steel wool goes into the holes first, then the spray foam. How do I stop the mice from pulling out the steel wool?
    – negacao
    Commented Mar 28, 2022 at 12:40
  • 1
    mice don't like to chew on steel wool, the foam keeps it in place. The other thing is that mice find the holes because of air movement, seal the leaks, they will be less likely to try to come in.
    – DaveM
    Commented Mar 28, 2022 at 12:41
  • 1
    You can leave a half-full bottle of vegetable oil open up there to clear out the mice; they crawl up and in to get the yummy grease, then get all slippery and stuck, eventually drowning. Discovered that in a painted-shut cabinet when I bought my house...
    – dandavis
    Commented Mar 28, 2022 at 12:52
  • 1
    Can you just apply some extra mortar? It looks like you've already got the holes plugged up from the image.
    – TylerH
    Commented Mar 28, 2022 at 17:50

2 Answers 2


Probably want metal flashing, but the best solution is to seal up all holes(1/4 inch and bigger ) to prevent them from coming into the house.

Will also need to get rid of all that are in the house now, you are only seeing part of them.

Contacting a pest control company in your area is a good idea.

  • I actually just sent one (pest control company) a message. I like the idea of flashing, but how do I seal up all holes (e.g. what material do I put in the actual holes)?
    – negacao
    Commented Mar 28, 2022 at 11:47
  • (and yes, the problem is much larger than the few mice I've seen on video. I suspect it's going to end up with hiring someone to remove the drywall from a few walls and ceiling, clean up all the inevitable mouse shit and corpses, replace the insulation and then put new drywall up.)
    – negacao
    Commented Mar 28, 2022 at 11:49

Copper wool/mesh is sold to plug small rodent holes. Steel wool rusts. Larger holes including slits and rectanguar openings can be fitted with 1/4 inch galvanized steel mesh (hardware cloth) and then spray foam.

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