How to Rodent-Proof Your Property: Practical Tips

Rodent-proofing — the physical exclusion of rats and mice from a building — is an important part of long-term rodent control. Bait and traps cannot prevent re-infestation if entry points remain open, and property owners can take practical prevention steps.

Understanding How Rodents Enter Buildings

Mice can squeeze through any gap as small as 6mm — roughly the diameter of a pencil. Brown rats (the most common species in London) need around 25mm — the size of a 10p coin. They are strong gnawers and will enlarge small gaps if they can detect warmth, food smells or a draught from the other side.

Common entry points in London properties include: - Gaps around water pipes, heating pipes and electrical conduits where they enter through walls - Air bricks with missing, cracked or mesh-free covers - Gaps at the base of external doors — particularly garage and outbuilding doors - Defective drains and sewer connections (rats can swim up soil pipes into properties) - Gaps in the roof line accessed from trees and climbing plants

Materials That Work — and Those That Do Not

Rodents will gnaw through: - Expanding foam alone (they can gnaw through it within hours) - Plastic mesh or netting - Thin sheet metal - Standard weather seals and draught excluders

Effective proofing materials include: - 25mm steel wool combined with expanding foam — the steel fibres deter gnawing - Ready-made wire mesh (19-gauge, maximum 6mm aperture) for vents and air bricks - Bristle strip draught excluders with a metal insert for door bottoms - Sheet metal kick plates on the base of external doors - Concrete mortar for gaps in brickwork

Room by Room: Where to Focus

*Under the kitchen sink* — the most common rodent entry route into houses. Pipes typically have a gap of 10–50mm between the pipe and the wall. Use steel wool and foam filler.

*Loft space* — inspect the entire perimeter at eaves level. Daylight visible from inside the loft indicates a gap. Pay particular attention to where the roof timbers meet the wall plate.

*External walls* — walk the outside of the building and probe any suspected gaps with a pencil. Mark gaps with chalk for reference.

*Drains and manholes* — ensure all drain covers are in good condition. Fit rodent-proof one-way valves (rat flaps) to drain inlets if drain entry is suspected.

A Note on Trees and Climbing Plants

Ivy and other climbing plants provide a ladder directly onto the roof. Squirrels, rats and mice all use them. Keep climbing plants cut back from roof level and ensure no tree branches touch or overhang the roof structure.

Ask a qualified operator whether professional proofing should form part of a treatment programme.