A small gap is enough
A young rat can squeeze through a gap of around 15mm — roughly the width of a thumb. The routes that matter are rarely dramatic holes; they are the small, overlooked gaps where services pass through walls, where materials meet, and where something has been damaged and never repaired.
Through the drains
Rats live in the public sewer and swim well. A defect in the private drain between a house and the sewer — a cracked clay pipe, a displaced joint, an old connection left open underground — lets them into the soil beneath the building. From there they reach floor voids and wall cavities. It is the most common route in Brent's Victorian and Edwardian terraces; our Kensal Green page explains why.
Rats coming up through a toilet are rare, but they do happen where drains are defective. Who owns which drain, and how defects are found, is covered in can rats enter through drains.
Gaps around pipes and cables
Wherever a waste pipe, gas pipe, boiler flue or cable passes through an outside wall, there is often a gap left around it. Kitchens and bathrooms are the usual culprits, especially after a new boiler or an extension.
Air bricks, doors and extensions
- Air bricks with broken or missing grilles, which open straight into the floor void
- Gaps under back doors and worn thresholds
- Cracks where a rear extension joins the original house
- Garage doors that do not close to the floor
- Holes left from old pipework that was removed
Up and over
Rats climb brickwork, drainpipes, trees and climbing plants, and can enter at the eaves or through gaps in a roof. This route is more common in houses with large gardens and trees; see rats in the loft.
Different homes, different routes
In the older south of the borough, drains and floor voids dominate. In the interwar houses of the north, gardens, decking and extensions play a bigger part — see rats in the garden. In blocks, it is bin stores and risers — see rats in flats.
Closing the route
Once the rats have been dealt with, the way in needs closing — otherwise they keep coming back. Drain faults need a drainage contractor. Small gaps can be sealed with our rodent proofing at £180 for up to one hour, and our rat proofing guide explains the options. To start, book rat control.
