How Are Mice Getting Into My House?

Start at ground level, outside

• Gaps under garage doors and worn or missing door sweeps.
• Utility penetrations: water lines, electrical conduit, gas lines, cable and AC line sets.
• Dryer vents with broken or missing flaps.
• Sill plate gaps where framing sits on the foundation.
• Mortar gaps and voids in fieldstone or block foundations.

Then look up

Rodents climb well. Damaged soffit corners, gable vents without intact screening, gaps behind fascia, and roof edges under overhanging branches all provide attic access. Attic activity often sounds heavier than it is because the noise carries across ceiling joists.

How to seal it so it lasts

Expanding foam alone does not stop rodents — they chew through it. Durable exclusion uses rodent-resistant materials such as copper mesh, hardware cloth, sheet metal or mortar, backed with sealant to keep out weather.

Sealing also has to be timed correctly. Closing every opening while animals are still inside pushes activity into wall voids, so removal and exclusion should happen together.

When it is worth having someone look

If you cannot find the opening, if activity is on more than one floor, or if you are dealing with an older home with many small penetrations, a systematic inspection of the exterior and attic will find things a spot check misses.