How rats get inside walls
In many London homes, rats inside walls are coming from the drains. Victorian and Edwardian houses often have old clay drain pipes under the floor. When a pipe cracks, or a redundant connection is left open after a bathroom or kitchen is moved, rats can climb out of the sewer into the space under the floor and up inside cavity walls. Other common routes are gaps around service pipes at ground level, broken air bricks, holes behind kitchen units and gaps where extensions join the original house.
Signs
- Scratching and scrabbling in one wall, especially near the kitchen or bathroom
- Noises in the ceiling below a bathroom
- A smell of rats or a sudden bad smell from a wall
- Droppings or gnawing near pipe boxing, under the bath panel or behind the boiler
Why poison alone is not enough
If rats are coming from the drains, baiting will kill some of them, but more will arrive along the same route. Dead rats inside walls also cause smells and attract flies. Finding and blocking the entry point is the real fix.
How we deal with it
- Inspect inside and outside to map where the noise is and where the rats could be entering
- Check drains and inspection chambers and look for open or redundant connections
- Treat with bait stations or traps in accessible voids
- Seal entry points and, where suitable, fit a rat blocker (non-return valve) in the drain
- Recommend a CCTV drain survey if we suspect broken pipes under the house
If a rat dies in the wall
The smell usually fades within one to three weeks as the body dries out. We can sometimes locate and remove it if it is accessible, and treat flies that may appear.
Questions and answers
Why do I hear rats in the walls but never see them?
They are travelling inside the cavity or under floors, often from the drains, and only come out where there is a gap.
What is a rat blocker?
A one-way flap fitted inside a drain pipe that lets waste flow out but stops rats swimming back up.
Do I need a drain survey?
If rats keep returning and drains are suspected, a CCTV survey shows whether a pipe is broken and needs repair.
Related pages
This page is general information, last reviewed on 19 October 2026. It is not a substitute for an on-site inspection.