How Do Rats Enter My Home in Cambridge?

Once you know there is a rat in the house, the next question is how. It matters because treatment clears the rats that are inside, but only closing the route stops the next one. The answer is rarely a single obvious hole by the back door.

From Below: the Drains

This is the route people least expect and the one most worth checking. Brown rats live and travel in the sewer system. Where a drain is intact they stay inside it. Where it is not, they come up.

• A cracked or broken section of pipe under the house or garden
• A joint that has pulled apart, often where tree roots or ground movement have shifted it
• An old branch left open or badly capped when a kitchen or bathroom was moved
• A missing or broken cover on an inspection chamber or rodding point
• A gully without its grid, or a disused toilet connection under a floor

Rats coming up this way often appear in a kitchen, bathroom or under-floor void with no gap anyone can find. Our post on rat blockers and drains explains what can be done when this is the route.

At Ground Level: Gaps in the Walls

BPCA give 15mm as the gap a rat needs to get into a structure, which is smaller than most people imagine. Common places at ground level include:

• Where services come in: gas, water, waste and cable entries, especially when the hole was cut larger than the pipe.
• Air bricks that are cracked, missing their grille or have been knocked out for a vent.
• External doors with a worn threshold, a missing strip or a gap under a garage door.
• Weep vents and cavity openings near the base of the wall that lead into the cavity itself.
• Extensions and conservatories where the new structure meets the old and a gap was left.

Through the Neighbours

Many Cambridge homes are terraced or semi-detached, with shared walls, shared lofts in some older houses, and connected under-floor spaces. A rat living next door can reach you without ever going outside. If your neighbour mentions rats, or you share a garden boundary with an outbuilding or compost heap they use, it is worth talking to them. A problem treated only on one side of a wall tends to come back.

From Above: Roofs and Climbing Routes

Rats climb well. Ivy and climbing plants on a wall, a drainpipe close to the eaves, or a tree branch touching the roof can lead to a gap under tiles or at the fascia. This route is less common for rats than for squirrels, but it explains some loft cases. Our post on rats in the loft covers that situation in more detail.

How to Check Your Own Property

A slow walk round the outside of the house tells you a lot. Take a torch and look low.

• Check every pipe and cable where it enters the wall, including behind the boiler flue and under the kitchen window.
• Look at each air brick for cracks or missing sections.
• Lift inspection chamber covers and look for droppings, debris or a damaged channel.
• Look for smear marks, which are dark greasy lines where rats brush the same edge repeatedly.
• Check under decking, sheds and the garage door for burrows or gnawed edges.

Do not seal what you find while rats are still active inside. A rat trapped in the building will gnaw out through something else, or die where it cannot be reached. The right order is to treat, confirm activity has stopped, then proof.

What We Do

Our rat control service includes a survey of how the rats are getting in as well as where they are active, including the drainage covers. Rat control is £260 with no call-out fee, and the rat control cost guide explains what that includes. Sealing the routes afterwards is rat and mice proofing at £180 for up to 1 hour, with any further time quoted before it is carried out. Where the route is a broken drain, the fix is a drainage repair and we will tell you so.

Find the route and you have found the reason they keep coming back.