Why proofing matters
If rodents can still get in, new ones will follow the same routes, guided by the smell trails left by the last ones. Proofing closes those routes. It is the difference between a problem that keeps coming back every autumn and one that is solved.
How small a gap do rodents need?
A young mouse can squeeze through a gap of about 6 mm, roughly the width of a pencil. A rat needs around 15 to 20 mm. Gaps that size are everywhere in older South London houses: around pipes, under floorboards, behind kitchen units, in cracked air bricks and where cables pass through walls.
Common entry points we seal
- Gaps around gas, water and waste pipes where they enter the building
- Holes behind kitchen units, under the sink and behind the boiler
- Cracked or broken air bricks and vents
- Gaps under doors and around garage doors
- Spaces under decking, sheds and conservatories that lead to wall cavities
- Damaged drains, open drain inspection chambers and redundant pipe runs
- Holes into ceiling voids and under-stair cupboards
Materials we use
We use materials rodents cannot chew through: wire wool packed with filler or cement, galvanised steel mesh, metal kick plates and bristle door strips, and rodent-proof air brick covers. Expanding foam on its own is not proofing; rats and mice chew straight through it.
Drains and rats
Many rat problems in London start in the drains. Rats can climb vertical pipes and get into homes through broken pipes under floors, uncapped redundant connections and open inspection chambers. We can fit rat blockers (non-return valves) and advise when a drain survey is needed.
What happens on a proofing visit
- We inspect inside and out to find every likely entry point, including routes in from next door
- We explain what needs sealing and agree the work and price with you
- We seal the gaps and fit any mesh, plates, brushes or covers
- We check for fresh activity on the follow-up visit
Questions and answers
Can I proof my home myself?
You can seal obvious gaps with wire wool and filler. The hard part is finding every route, including those under floors and behind units, which is where an inspection helps.
Does proofing come with treatment?
Usually both are needed: treatment for the rodents already inside, and proofing to stop new ones. We can do both on the same visits.
Do you fit rat blockers in drains?
Yes, where the drain is suitable. If the drain is damaged, we will recommend a drain survey or repair first.
How long does proofing last?
Properly sealed gaps last for years. New gaps can appear after building work, so it is worth checking after any alterations.
Related pages
This page is general information, last reviewed on 19 October 2026. It is not a substitute for an on-site inspection.