Moisture seekers: how slugs find their way into UK homes

Written by Avon Pest ControlFirst published 15 March 2024Updated 9 November 2026

A slug on the kitchen floor is unpleasant. A slug in an upstairs bathroom is baffling. Both come down to the same thing: slugs need moisture, they are very good at squeezing through small gaps, and they climb.

The short version

• Slugs come indoors for moisture and shelter, mostly at night and in wet weather.
• They can squeeze through gaps of only a few millimetres and climb walls, pipes and cavities.
• Following the slime trail back, usually to a gap at floor level or around pipework, finds the way in.

How slugs enter homes

Slugs dry out easily, so they look for cool, damp, sheltered places. At night, and after rain, they move around a lot, and a house with a gap at ground level is an easy place to end up. Having no shell, they can flatten and stretch their bodies to fit through openings that look far too small.

The common routes in are:

• Gaps under external doors and worn thresholds.
• Air bricks with no mesh, which lead into the void under a suspended timber floor. From there slugs come up through gaps in floorboards and behind skirting.
• Gaps around waste pipes, water pipes and cables where they pass through the wall, especially behind kitchen units and washing machines.
• Cracked brickwork, failed pointing and gaps around window and door frames.
• Cellars and damp under-stairs cupboards with an opening to the outside.

The unusual journey upstairs

Slugs climb well. Their mucus lets them grip vertical surfaces as well as glide over flat ones, so a wall, a downpipe or the inside of a cavity is no barrier. Slugs found upstairs have usually come up inside the house rather than over the outside: through wall cavities, alongside pipe runs or the soil stack, or through gaps where pipes pass through floors.

Bathrooms attract them because they are the dampest rooms in the house. A bathroom with a slug problem often has a gap around the bath waste, toilet pipework or boxing-in, and frequently some damp or a slow leak in the same area.

Slugs as pests

Slugs are not a direct risk to people, but they are unwelcome indoors. Their trails mark carpets and floors, they can contaminate surfaces where food is prepared, and they eat pet food left down overnight. Slugs and snails can also carry lungworm, a parasite that can be serious for dogs that eat them, which is one more reason to keep them out of the house and away from pet bowls.

Indoors they are a nuisance rather than a threat to the building. A steady supply of slugs does, though, usually mean damp or a gap that is worth fixing in its own right.

Managing slug invasions

• Find the route. Go round with a torch after dark, or look first thing in the morning, and follow the fresh trails back. They usually lead to one or two specific gaps.
• Seal entry points. Use sealant or expanding foam around pipes, brush strips on doors, and fine mesh over air bricks without blocking them.
• Reduce moisture. Ventilate bathrooms and kitchens, fix leaks and dry out damp areas.
• Remove what attracts them. Do not leave pet food down overnight, and clean up spills and food waste.
• Make the outside less inviting. Move plant pots, logs and dense planting back from the walls, where slugs shelter during the day.

For removing the slugs you already have, see how to manage indoor slugs safely. For stopping them for good, see slugs in the home: causes and long-term fixes.

When to call us

If you cannot find how they are getting in, or they keep coming after you have sealed the obvious gaps, we can trace the route and recommend proofing. Where the cause is a leak or damp, a plumber or builder is the person to fix it, and we will say so.

Removing slugs safely → Long-term fixes →