Rat and mouse articles · Updated
Mice in the walls: how to find them and stop them
Mice in the walls are traveling between the garage, the attic and the kitchen along pipes and wires. Trap where they come out of the wall, under sinks, behind appliances and in the garage and attic. Then seal the pipe and wire gaps and the outside entry point.
Light scratching inside the wall after the house goes quiet. A quick run along the ceiling over the kitchen. In a Plano house, that's usually house mice using the wall cavities as hallways. They don't live in the drywall itself; they move through the gaps around pipes, wires and ducts, and nest wherever there's soft material near food.
You can't trap mice inside a closed wall, and you don't need to. You trap them where they come out, then close the gaps.
Is it mice?
Mice make light, quick, scratchy sounds that move along the wall. Roof rats sound heavier and are more often overhead. Squirrels are loud in daylight. Insects like crickets or wood-boring beetles make clicking or ticking sounds, not scurrying. If the sound is light, at night and near the kitchen, the garage or a bathroom, mice are the likely answer.
Narrow down the spot
Spend a few nights taking notes. Write down which wall, how high the sound is, what time it starts and whether it moves. Then look at what's on either side of that wall.
- A wall shared with the garage: mice are coming in from the garage along pipes or wires
- A wall behind the kitchen sink, stove or fridge: they're using the plumbing and gas penetrations
- A wall below a bonus room or knee wall: they're coming down from the attic
- A bathroom wall: they're using the plumbing chase between floors
Something in the attic or the garage?
Want a local rodent technician to look at it? Same-day appointments are often available. (972) 325-9652
Find the droppings
Droppings show the route. Check under the nearest sink, behind the stove and fridge if you can pull them out, along the garage wall on the other side and in the attic above. A line of droppings along a pipe or the top of a wall tells you exactly where they travel. The droppings article explains how to read and clean them.
Trap where they come out
Set snap traps flush against the wall where the mice leave the cavity: under the sink near the pipes, behind the stove, along the garage wall and in the attic along the top plate. Texas A&M AgriLife training material suggests using plenty of traps for mice, several per mouse, a few feet apart, and checking them often. Bait with a small dab of peanut butter or a little nesting material like cotton.
Don't put poison in the walls or attic. A poisoned mouse can die inside the cavity where you can't reach it. The traps article covers types and placement.
Seal both ends
Once the catches slow down, close the gaps inside: pack copper mesh or steel wool around the pipes under the sink and behind appliances, then seal over it. Then close the outside entry that let mice reach the cavity in the first place. In Plano that's usually the garage door seal, the AC line set or an open weep hole. AgriLife's material says a mouse only needs a quarter-inch crack.
How fast it grows
Texas A&M AgriLife's rodent training material warns that a single pair of mice can become an infestation quickly. That's why waiting it out rarely works. A few mice in the wall in November can be a lot more by spring if they have food and nesting material. Start trapping as soon as you're fairly sure it's mice.
Cut off the food in the kitchen
Mice in the walls are usually there for the kitchen. Make it less rewarding while you trap:
- Move cereal, crackers, flour, rice and pet food into hard containers with tight lids
- Wipe crumbs off counters and the floor under the toaster every night
- Don't leave pet bowls out overnight
- Empty the kitchen trash before bed
- Check the back of the pantry and the drawer under the oven for droppings each week
Garage first
In most Plano houses, mice reach the walls from the garage. Before you focus on the noisy wall, check the garage: the bottom door seal, the corners of the door, the gap around the water heater flue and the wall shared with the house. Droppings along that shared wall or on top of the water heater confirm the route. Sealing the garage often does more than anything you do inside.
Why it happens in Plano houses
Two-story Plano houses have long wall runs and plumbing and HVAC chases that connect the garage, the first floor and the attic. Houses with a bonus room over the garage are especially prone, since the knee walls beside that room open into the garage attic. Mice can go from the garage to an upstairs bathroom without ever crossing an open floor. That's why the sound can seem to come from a room far from where they got in.
When to call
If the noise keeps going after a couple of weeks of trapping, or you can't find where they're getting in, a technician can trace the route. Mice in the walls removal explains what a thorough job includes.
Something in the attic or the garage?
Ready to have the gaps found and closed? Call and describe what you're hearing or finding. (972) 325-9652
Common questions
Will the mice leave on their own?
Not if they have food and nesting material nearby. They usually stay and breed.
Do I need to cut open the wall?
Rarely. Trapping where they come out and sealing the gaps handles most cases.
What if the noise stops and a smell starts?
A mouse may have died in the wall. See the dead rodent smell article.
Can mice chew wires inside walls?
They can gnaw on wiring. If a breaker trips often or you smell burning, call an electrician.
Can I use poison bait in the garage instead?
Poisoned mice can still die inside the walls next to the garage. Traps are a better choice indoors and in an attached garage.