How Are Mice Getting Into My House?

By Exterminate Pest Control

You’ve caught a mouse under the kitchen sink. A week later, there are fresh droppings in the same cupboard. Where are they coming from? The answer could be a pencil-width gap behind the kitchen units, an opening around the boiler pipes, or a hidden route from the house next door.

House mice can squeeze through a hole about 6 mm wide and climb rough brickwork and timber. That gives them access to parts of the house you might never think to check, from the gap behind your washing machine to the soffits above your bedroom. If mice keep coming back, start by working out where they’re getting in.

Can Mice Come Into My House From Next Door?

Yes. In terraced houses, semi-detached homes and apartment blocks, mice can move between properties where gaps connect wall cavities, roof spaces or service routes. A mouse may enter the building through one property and turn up in another, sometimes a floor away from where it first got in.

This is one way a secondary mouse infestation can develop. An existing mouse problem in one part of a building spreads into another through a connected route. Common places to investigate include:

• Shared walls where there are unsealed openings around pipes or cables.
• Boxed-in plumbing and service ducts that connect floors or flats.
• Gaps beneath kitchen units where waste pipes disappear into a wall or floor.
• Adjoining roof spaces where gaps allow movement between properties.

If you find droppings along a shared wall, hear scratching near a pipe duct, or discover that several homes in the same building have mice, a connected route is worth investigating. The signs alone can’t tell you which property the mice entered first. In an apartment block or rented property, report where you’re seeing activity to the management company or landlord so any shared spaces can be checked.

Can Mice Get In Around a Boiler?

Yes. Check where the boiler pipes pass through the wall or floor. A warm, quiet boiler cupboard or hot press can offer shelter, and an opening around the pipework can give mice a way in. The same applies to utility rooms where several pipes and cables pass through an outside wall. Even if the opening looks tidy at the front of the cupboard, there may be a gap hidden behind it.

If you find droppings beneath a boiler, look for visible gaps around the nearby pipework from both sides of the wall where you can safely access them. Keep boiler flues and required ventilation openings clear. If proofing could affect a gas appliance, its flue or its ventilation, consult a Registered Gas Installer.

Can Mice Climb Walls and Get Into the Attic?

House mice can climb rough brick, concrete and timber. They can also use pipes, cables and climbing plants where they can get a grip. Once they reach the roofline, a gap at the eaves, a damaged soffit or an opening around an attic vent can give them access to the roof space. 

If the first sign you notice is scratching above the bedroom ceiling at night, look at the outside of the house from ground level. Check for visible damage along the roof edge and note any ivy or cables that reach it. A mouse can also climb through a connected void inside the building, so attic activity is a reason to check both the roofline and the routes leading up from below. 

Where Should I Look for Mouse Entry Points?

Start where you’ve seen droppings, gnaw marks or damaged food packaging. Then follow nearby walls and pipes to see where they lead. A mouse seen in the kitchen may have travelled there from a wall cavity or utility room.

Where you see signs

Where to look for a route

Under the kitchen sink

Around the waste pipe and water supply pipes where they enter the wall or floor

Behind the washing machine

Around the drain hose, service pipes and cable openings

In a boiler cupboard or hot press

Visible gaps where heating pipes pass through walls or floors

Along a wall shared with next door

Pipe and cable openings, boxed-in services and gaps at floor level

In the attic or upstairs ceiling

Soffits, eaves, attic vents and service routes leading up from lower floors

Near a back door or garage

Worn door seals, gaps at thresholds and openings around nearby services

These are places to inspect. Fresh droppings near an opening can help narrow the search, especially when the same spot shows activity repeatedly.

Why Do Mice Keep Coming Back After I Catch Them?

An open entry point can allow more mice in, and there may still be mice in a wall cavity, attic or other sheltered part of the building. That’s why effective mouse control combines treatment for the active infestation with proofing to close the routes mice use. If those routes connect several properties, the inspection may need to include shared areas.

The right repair depends on the opening. A damaged door seal needs a different fix from a gap in masonry or an opening around a service pipe. Mice can gnaw through ordinary expanding foam, so foam alone is a poor choice for a gap they already use.

Book a Mouse Inspection With Exterminate Pest Control

If mice keep returning, tell us where you found the droppings, when you hear scratching, and whether nearby homes have reported activity. Those details can help narrow down where to look, whether it’s the pipework behind the boiler, the roofline or a route between properties.

Contact Exterminate Pest Control through Exterminate.ie or call us on 0852635994 to arrange a mouse inspection and get advice on treatment and rodent proofing.