How do I keep mice out in winter?
The short answer
Do the sealing in early fall, before the first cold snap moves them in. Seal every gap wider than a pencil around utility penetrations, vents, garage door seals and the roof line, cut back vegetation touching the building, and get food sources — including pet food and bird seed — into sealed containers.
The fall checklist
- Walk the exterior at ground level and again looking up at the roof line. Gaps at pipe and cable penetrations, dryer vents, gable vents and where the siding meets the foundation are the usual entries.
- Check the garage door seal along the bottom and at the corners, which is one of the most common entries and the easiest to fix.
- Cut back branches touching the roof and climbing plants on walls. Roof rats and squirrels use them as a bridge.
- Store pet food, bird seed and grass seed in sealed containers, not in the original bag.
- Move woodpiles away from the building and off the ground.
The usefulness of doing it early is that an empty building is far easier to seal than an occupied one. Once rodents are inside, sealing traps them in, so the order becomes trap first and seal afterwards — which takes longer and costs more.
Expanding foam alone is not a rodent seal. Mice chew through it readily. Use it as a filler behind hardware cloth or sheet metal, not as the barrier.
Also asked
- Do ultrasonic repellers work?
- The published evidence does not support them for rodents in a real building. Rodents habituate, the sound does not pass through walls or furniture, and testing has repeatedly failed to show a durable effect. Money spent on sealing the gaps does what the device claims to.
Companies whose reviewers name rodents
5,287 pest control businesses in the United States and Canada have reviewers who write about rodents. Every listing shows the full rating distribution rather than the average, the share that is one or two star, and whether the owner replies.
Read next
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General information about pest problems and about hiring, not advice about your specific property. Pest control licensing, wildlife protection and landlord and tenant law are all set state by state and province by province across the United States and Canada, so your own regulator is the current answer. How we read the data.