Rodent-proofing a home

Start with the gaps, not the traps

Trapping deals with the rodents that are already inside. It does nothing about the route they used, which means the next one comes in the same way.

The measurement worth remembering is small. A young rat needs a gap of roughly two centimetres and a house mouse needs about half of that. Hold a pencil to a gap. If the pencil fits, so does a mouse.

Work around the outside of the building once, slowly, with a torch. What you are looking for is light, draught and rub marks rather than the animal itself.

Where they actually get in

The recurring ones are the gap under an external door, the hole cut for a waste pipe or an air conditioning line and never filled, a vent with a missing cover, a roof edge where the sheet meets the wall, and the run where a cable enters the building.

Fill small holes with steel wool packed tight and sealed over, or with mortar. Rodents gnaw through expanding foam and plastic on their own, so neither works alone.

Fit a brush strip or a metal kick plate to a door with daylight under it. Cover open vents with fine metal mesh rather than plastic mesh.

Trim any branch that touches the roof, and pull climbing plants back from the wall. Rats climb well, and a branch is a bridge.

Take away the reason to stay

A sealed building with food left out is still an attractive building. Keep grain, flour and pet food in rigid containers rather than sacks, and keep them off the floor.

Bin bags left standing overnight, fruit fallen behind the store, animal feed in an open bag and water in an uncovered drum are all reasons to persist.

Clear the run of clutter along the walls, inside and out. Rodents move along edges and dislike crossing open ground, so a clear metre against a wall is genuinely a deterrent.

When something is already inside

Once the building is closed, deal with what is left indoors. Place glue boards flat against the wall, in the run rather than in the middle of the room, and along the route where you have seen droppings or rub marks.

Place them out of reach of children and pets. Behind a cupboard, under a unit or inside a store is both safer and more effective, because that is where the rodent is walking anyway.

Check them daily. A board left unchecked is unpleasant for everyone and it is also a board that stops working.

Wear gloves to handle and dispose of a used board, seal it in a bag, and wash your hands afterwards.