Mice in the Walls: Signs, Causes and How to Get Them Out

If you hear light scratching, rustling or squeaking inside a wall at night, you probably have mice. They nest in wall cavities and come out to feed, usually in the kitchen. To get them out, set traps where they leave the wall, often under the sink or behind appliances, and seal the gaps outside where they get into the house. Opening the wall is rarely necessary.

Older Cleveland homes are especially prone to mice in the walls because of how they were framed. Here is how to confirm it and fix it.

Signs of mice in the walls

• Scratching, scurrying or light gnawing inside a wall or ceiling, mostly from dusk to early morning
• Sounds that move along the wall or from room to room
• Droppings near baseboards, under sinks, behind appliances or in drawers near that wall
• Small holes at the base of the wall or around pipes
• A musty smell in one area
• A pet staring at or sniffing one spot on the wall

Mice sound light and quick. Rats sound heavier, with thumps and dragging, and in Cleveland they usually stay lower in the house. Daytime noise in the attic is more often squirrels.

Why Cleveland walls fill up with mice

Many Cleveland houses built before about 1930 are balloon-framed. The wall studs run from the foundation sill to the roof without breaks between floors, so the wall cavity is an open shaft. A mouse that enters at the sill can climb to the second floor or the attic inside the wall.

Plaster and lath walls add footholds and gaps. Radiator and steam pipes run through floors in holes that are often wider than the pipe. In doubles, mice travel through shared walls and the shared basement between units.

The fall cold pushes mice indoors, and an old house with gaps at the sill, the foundation and the utility lines lets them in. The CDC notes a mouse can fit through a hole about a quarter inch wide.

Trap at the exits

Mice have to leave the wall to eat and drink, and they use the same routes every night. Find those exits:

• Gaps around pipes under the kitchen and bathroom sinks
• Behind the stove, refrigerator and dishwasher
• Holes around radiator pipes
• Gaps at baseboards and trim, especially in closets
• The basement sill directly below the wall

Set snap traps close to those spots, against the wall, with the bait end toward the wall. The CDC recommends snap traps and a small amount of a sticky bait like peanut butter. Use several traps a few feet apart. Check them daily.

Seal from the outside

Trapping without sealing means new mice replace the ones you catch. Walk the outside of the house and look at:

• The sill line where the wood frame meets the foundation
• Gaps around gas, water, cable and air conditioning lines
• Dryer vents and other vent openings
• Garage door seals and side doors
• Porch and addition joints

Pack small gaps with copper or stainless mesh and seal over them. Use hardware cloth or sheet metal for larger openings. Once the traps stop catching, seal the interior exits too.

Mice in the walls of a double or apartment

In an up-and-down double or a small apartment building, the mice in your wall may be living in the shared basement or in the other unit. Trapping in one kitchen helps for a while, but mice from next door keep replacing them. The lasting fix covers the shared basement, the pipe chases between units and the outside of the building.

If you rent, tell your landlord in writing and describe where and when you hear the noise. Ohio law requires landlords to keep common areas safe and sanitary and the premises fit and habitable. Our tenant and landlord guide explains the steps.

What not to do

• Do not put poison in the walls. Poisoned mice often die inside the wall and cause a smell that lasts for weeks. See dead rodent smell.
• Do not rely on ultrasonic plug-ins. The FTC has warned sellers that efficacy claims need scientific support.
• Do not seal every gap while mice are still inside without trapping. They may chew new exits into rooms.
• Do not open the wall unless you have to. Traps at the exits work in most homes.

When to call a technician

Call if the noise continues after two weeks of trapping, if you hear mice in several walls or floors, if you find droppings in more than one room, or if you cannot find where they enter. A technician can trace routes through balloon-framed walls and seal the entry points you missed. See mice in walls removal.

Frequently asked questions

Sources

• CDC: How to Seal Up to Prevent Rodents
• CDC: How to Trap Up to Remove Rodents
• FTC: FTC Warns Manufacturers and Retailers of Ultrasonic Pest-control Devices (2001)

Related reading

• Mice in Walls Removal in Cleveland
• Mice Exterminator in Cleveland
• Rodent Noises at Night: What You Are Hearing and Where
• Dead Mouse or Rat Smell: How Long It Lasts and What to Do
• Rodent control in Cleveland Heights