Mice Entry Points: How to Find Where Mice Are Getting Into Your House

Mice get into houses through gaps of about 5 mm, the width of a pencil. The usual ways in are gaps around pipes and cables, broken air bricks, gaps under outside doors, and the roofline. To find yours, start where the droppings are freshest and work out to the nearest outside wall.

New to mice in the house? Start with our guide to mice in UK homes.

How do mice get into houses?

These are the mice entry points our technicians check first. Most are at ground level, but mice also climb to the roofline.

Mice avoid open ground. Plants, bins or stored wood against a wall give them cover right up to a gap. Most move in from early autumn: here’s what time of year mice come inside.

How small a gap can a mouse get through?

About 5 mm. If you can push a pencil into a gap, a mouse can get through it. A hole mice use regularly is usually bigger, about 2–3 cm across, with dark smear marks around the edge.

How to find where mice are getting in: 6 checks

1. Start inside, where the signs are freshest. Follow fresh mouse droppings and smear marks along the skirting to the nearest outside wall, pipe or unit. Wear gloves, as rodents can carry diseases.
2. Pull out the kitchen appliances. Most mouse problems start in the kitchen, under the sink and behind the washing machine. Look where pipes and cables leave the room. If the gap leads into a wall or behind units, see how to get mice out of the walls.
3. Walk round the outside at ground level. Use a torch, even in daylight. Check every pipe and cable entry, air brick and door bottom, and the base of the walls and steps.
4. Look up. Check the eaves and anywhere climbing plants, ivy or trees touch the house. Mice climb up plants to reach the loft.
5. Check the garage and anything you share. Look where pipes and cables pass through a wall shared with an attached garage. In a terrace or semi, the gap may be on your neighbour’s side, so ask them to check too.
6. Test a hole before you seal it. Push a loose ball of paper into it and look again the next morning. If it’s been pushed out or chewed, mice are using it. To see which way they run indoors, sprinkle talcum powder or flour on the floor to see if there are any mouse tracks or footprints.

How do mice get into the loft?

From outside, mice climb plants, pipes and rough brickwork to the eaves, then slip through gaps in the soffits or where the roof meets the wall. In a terrace, they can cross from next door’s loft through gaps in the shared wall. The pipes and cables that run up from the kitchen or bathroom are the other way in.

Not sure it’s mice up there? See what kind of animal is in your attic.

Block mouse entry points and stop mice getting in

Seal every gap on the outside of your home as soon as you find it, since a mouse only needs about 5 mm. Pack gaps around pipes and cables with wire wool and finish with quick-setting cement, because mice chew through expanding foam on its own. Fit a brush strip under outside doors. Cover air bricks and vents with fine metal mesh instead of blocking them. To get rid of mice, cut back plants touching the walls, and leave holes inside the house until your traps stay empty.