Why building work causes pest problems
- Disturbed rodents: demolition, groundworks and drain work displace rats and mice living under floors, in old drains or in neighbouring buildings
- New gaps: holes for pipes, cables and vents are not always sealed properly when work is finished
- Redundant drains: when a kitchen, bathroom or WC is moved, the old drain connection may be left open under the floor, giving rats a route from the sewer
- Hidden voids: new boxing, plinths and false walls create voids where pests can live unseen
- Imported insects: grey silverfish and other insects can arrive in building materials and packaging
What to ask your builder
- Cap all redundant drain connections properly
- Seal gaps around new pipes, cables and vents with rodent-resistant materials, not foam alone
- Keep air bricks clear and fit covers if they are damaged
- Leave access to under-floor voids where possible
- Clear food waste from site daily
After the work
If you notice droppings, gnawing, scratching or new insects after building work, act early. We inspect, treat and proof, and can check drains for open connections. If neighbours are building, the same can happen to you, as disturbed rodents move next door.
Contractors
For demolition and major works, see pest control for building sites.
Questions and answers
Why have I got rats after my extension?
Usually because a drain was disturbed or left open, or gaps were left around new pipes. An inspection can find the route.
Can my neighbour's building work cause pests in my home?
Yes. Disturbed rodents often move into neighbouring properties.
What are grey silverfish?
A newer species, common in new builds, that arrives in materials and packaging. See our silverfish guide.
Related pages
This page is general information, last reviewed on 19 October 2026. It is not a substitute for an on-site inspection.