Dealing with mice right now? Mouse & Rat Control, by a team that does nothing else.
People look for a hole. What is actually there is usually a gap that was made deliberately, by a plumber, an electrician or a builder, and then never sealed. Once you know the list it becomes obvious, and most of it can be checked in half an hour with a torch.
The number that matters
An adult house mouse passes through roughly 6mm, about the width of a pen. A young one needs less. A mouse cannot chew through steel or mortar, but it will readily enlarge a gap in anything softer, so a 4mm crack in old mortar is a 10mm hole a fortnight later.
This is why properties that look sound still let mice in. Nobody is missing an obvious hole. They are missing ten small ones.
The routes we find most
- Pipe runs behind kitchen units. The hole cut for gas, water or waste, almost never sealed afterwards, and hidden behind the plinth. This is the one, more than any other.
- Behind the bath panel. Same problem upstairs, with the added advantage to the mouse of a route between floors.
- Air bricks with broken or missing slats. Straight into the underfloor void.
- Worn door thresholds. Particularly back doors, garage side doors and anything with a rubber seal that has perished.
- The eaves. On a lot of 1930s housing the detail at the wall plate leaves a continuous open gap along the roof line.
- Open cavity heads. The top of a cavity wall, often open into the loft, and in terraces continuous with next door.
- Extension junctions. Where a newer roof meets the original wall, and where a new floor slab meets old brickwork. Rarely sealed to rodent standard.
- Garage conversions. The old threshold line, and the gap where the new floor was laid over the old one.
- Soil pipe boxing. A vertical shaft between floors that is frequently open at both ends.
- Meter boxes and cable entries. Small, tidy, and usually straight into a cavity.
Why the entry point is rarely near the droppings
Mice follow edges. They run along skirting, joists and cable runs rather than crossing open floor, so the place you find droppings is a feeding or nesting area, not necessarily an entrance. A kitchen full of evidence often has its entry point in the underfloor void two rooms away.
Working back from the evidence to the entry is most of the skill in a survey. Following the run rather than treating the room is the difference between a job that holds and one that repeats.
How to check your own property
None of this is a treatment, but it will tell you a lot before anyone visits:
- Take the plinth off the base units and look at every point where a pipe enters
- Take the bath panel off and do the same
- Walk the outside of the building slowly, at ground level, looking at air bricks and thresholds
- Look up at the eaves and the point where any extension meets the original wall
- In the loft, look at the tops of the cavity walls and along the wall plate
A torch held flat against a wall throws long shadows and shows gaps you will not see straight on.
Sealing it properly
Expanding foam, plastic and sealant on their own are not proofing. Mice chew through all three. What holds is stainless steel wool packed tight, rodent mesh, metal plate, cement mortar and rodent-proof brush strip on doors. Ventilation openings are meshed rather than blocked, because trading a rodent problem for a damp one is not a fix.
If there are mice in the property now, treat first and seal afterwards, or you seal them in. See mice proofing for the detail, super-proofing for whole-property work, and mouse control for how a full job runs.