The house mouse copes well outdoors in the warm months: gardens, embankments, plant rooms, underground networks. When temperatures drop, it moves closer to heated buildings with plenty of food. A house, a ground-floor flat or a shop's stockroom then becomes an ideal refuge.
If mice turn up at the same time every year, they are usually not the same animals: they are newcomers using the same way in. So the problem to solve is first and foremost a problem of gaps.
Checking the entry points, room by room
A mouse fits through a hole you could barely slide a pencil into. During the inspection, these are the places we look at first:
- Kitchen: water supply and waste pipes under the sink, behind the oven and fridge, loose skirting boards.
- Utility room, boiler room: pipe penetrations for the washing machine and boiler, ventilation ducts.
- Garage, cellar, basement: doors without a seal at the bottom, basement vents, cable ducts through the slab.
- Walls and roof: damaged air bricks, roller-shutter boxes, joints between wall and roof.
- Shops and restaurants: stockroom, delivery bay, service ducts and suspended ceilings shared with neighbouring units.
Materials that really hold
Expanding foam on its own does not last: mice chew through it in a few nights. Effective proofing combines a material they cannot gnaw (steel wool, fine metal mesh, sheet metal) with a mortar or sealant that holds it in place. Around pipes, a collar or metal plate closes the ring-shaped gap; under doors, a brush or rubber door sweep removes the slit.
In the Sentinel Protocol, this work belongs to the "Sanitise" stage. It is done once the mice already inside have been dealt with and their routes confirmed, so none get shut inside the walls.
When to act to stay ahead
Late summer is the ideal time to inspect and proof, before pressure builds with the first cold nights. Meanwhile, a few habits make your home less attractive: food and pet food in airtight boxes, closed bins, no cardboard boxes stored on the cellar floor.
For a co-owned building, shop or restaurant, a prevention plan organises regular visits, checks on sensitive points and active vigilance all year round, with a report after each visit.
Key points
- 01It is rarely the same mice: it is the same gaps.
- 02About 6 mm is enough for a mouse to get in.
- 03Steel wool or mesh plus mortar or sealant: foam alone does not last.
- 04Inspecting and proofing in late summer keeps you a step ahead.
This article gives general information, up to date on its publication date. It does not replace legal or medical advice tailored to your situation.