In short
When temperatures drop, mice look for warm shelter and food, and get in through gaps of around 6 mm around pipes, cables and under doors. If those gaps stay open, every autumn brings new mice, even after a successful treatment. The lasting fix is to find them and seal them with materials mice can't gnaw through.
We see this pattern often: an effective treatment in spring, a quiet house all summer, then scratching in the walls on the first cold nights. Last winter's mice are gone, but the neighbourhood's mice have found the same way in.
Where do they get in?
A mouse can squeeze through a gap of about 6 mm. Entry points are rarely dramatic: they are construction details nobody looks at.
- Pipe openings under the sink, behind the washing machine or the boiler.
- Cable ducts and conduits running through walls or floors.
- Garage, cellar or front doors without a seal at the bottom.
- Damaged air vents, drain holes, roller-shutter boxes.
- Joints between wall linings and skirting, false ceilings open onto common areas.
How to proof for good
Expanding foam on its own doesn't work: mice chew through it. We combine steel wool or fine mesh with mortar or sealant, fit collars around pipes, brush or rubber door sweeps and metal grilles over vents.
This is the Lock step of our method. It is done once the real routes are known, so no mice are trapped inside.
Getting the timing right
The best time to inspect and proof is late summer, before the first cold spell. For a block of flats, a co-ownership or a business, a prevention contract includes regular visits and monitoring of sensitive points all year round.
Key points
- Mice get in through gaps of around 6 mm.
- Pipe and cable openings are the most common entry points.
- Foam alone won't hold: combine steel wool, mesh and mortar or sealant.
- A late-summer inspection prevents the autumn invasion.
General information, correct at the date of publication; it does not replace personal legal or medical advice.