How Do You Know If You Have Rats Under the Floorboards?

Why Under the Floor Suits Them

A Victorian or Edwardian house with a suspended ground floor has a ventilated void beneath it — dry, dark, undisturbed, and connected to the outside by air bricks and to the rest of the house by every pipe that comes up through the boards.

It is also directly above or beside the drainage, which is where most of our rats come from. A rat that gets into the drains and out through a defect frequently ends up in that void without ever going outside.

What You Hear, and When

Scratching and scurrying from below rather than above, usually after dark and often loudest in the hour or two after the house goes quiet. It sounds like it is coming from under your feet or from inside the wall at floor level.

Weight is the clue that separates rats from mice. A rat sounds like something being dragged or a distinct heavy scurry; mice are a lighter, faster rustle. If you can hear gnawing through a carpet, that is generally a rat.

What You See Without Lifting Anything

Droppings appearing at the edge of a room, behind a sofa or inside a low cupboard. A greasy dark smear where the skirting meets the floor. Gnawing at the bottom corner of a door frame or a skirting board. Disturbed insulation pushed up between boards.

The airing cupboard and the space under the stairs are worth a proper look, because both usually have an unsealed penetration straight down into the void.

The Smell Test

An occupied floor void develops a distinct stale ammonia smell that comes up through gaps between the boards, strongest in a room that is shut up. People often describe it as a damp or drain smell and get a plumber out first.

If a room smells and you cannot find a source at eye level, get down and smell at the skirting line. It is an unglamorous test and it works.

Check the Air Bricks Before You Lift a Board

Go outside and look at every air brick around the base of the building. A broken grille, a missing brick, or one that has been rendered over and cracked is the usual way in, and it is far easier to find from the garden than from inside.

Then look at the inspection chamber if there is one. A damaged benching or an uncapped redundant connection is the other half of the answer. Do not seal anything yet — proofing an occupied void seals rats under your living room.