Getting Mice Out of Walls and Ceilings

Scratching inside the wall after dark is one of the most common reasons people call. Mice use wall voids and ceiling cavities as hallways, moving from a gap at the foundation up to the kitchen or attic. You hear them because the house is quiet and they're busy.

The fix has two parts: catch the mice where they come out of the wall, and close the gap where they come into it. Cutting into walls is rarely needed.

Here's what a wall job tends to cover:

• Listening and looking for where noise and droppings concentrate
• Checking openings into the wall: pipe holes under sinks, behind the stove and washer
• Traps set at those exit points and in the attic or garage
• Sealing pipe and wire penetrations inside the house
• Sealing the outside entry, usually low on the wall or at the garage
• Odor handling if a mouse died inside the wall

Mice in a wall have to come out to eat. The technician finds where: the gap around the pipes under the kitchen sink, the hole behind the dishwasher, the opening where the dryer vent passes through, the top plate in the attic. Traps go there. Inside openings get sealed with metal or hardware cloth after the catch stops.

Outside, the technician follows the wall down to find how mice got in, often at the weep screed where stucco meets the foundation, at a hose bib or at a garage corner. That gap gets sealed last. If a mouse dies inside the wall, see dead rodent and odor removal.

Frame-and-stucco walls have a gap between the foundation and the bottom of the stucco, and settling widens it. Block houses have hollow cores that connect across a wall. Older homes in the University area and Nob Hill may have plaster walls, floor furnaces and old wiring holes. Each gives mice a protected route. Flat roofs add a ceiling cavity that connects to every interior wall.

Noise also travels. A mouse on the roof parapet can sound like it's in the bedroom wall. A good inspection sorts that out.

The sound tells you a lot:

• Light scratching and scurrying at night: likely mice
• Heavier movement, things being dragged: possibly a pack rat
• Daytime noise high in the house: could be birds or squirrels
• Steady tapping in one spot: sometimes a pipe, not an animal

Don't put poison in the wall. The mouse may die inside, and then you have a smell to deal with. Don't stuff the inside openings with steel wool or foam while mice are still in the wall, since they'll chew out somewhere else. Don't cut holes to chase noise. Find the exit points first.

Ask how they plan to handle wall activity before they start:

• Where do you think they're coming out of the wall?
• Where will traps go, and how often will you check them?
• What will you seal inside the house, and what outside?
• Will you check the attic and the roofline?
• What happens if one dies in the wall?

Noise in a wall isn't always mice. Pack rats, birds on the roof and even ductwork expanding in the heat make sounds, so an inspection should sort that out before anyone sets traps.

Once it's confirmed, sealing has two halves. Inside sealing stops mice coming out into the kitchen; outside sealing stops them coming into the wall at all. A job that does only one side tends to come back.

• Saw One Mouse? Here's How to Tell If It's Alone
• Mice in Adobe and Stucco Homes: Finding and Closing the Gaps
• Mice in the Kitchen: What to Throw Out, Clean and Seal

Related services: House Mouse Control / Dead Rodent and Odor Removal / Sealing and Exclusion

Calls come from Northeast Heights, Sandia Foothills and North Albuquerque Acres, High Desert, Sandia Heights, Nob Hill, University Area, Southeast Heights, International District, Uptown, Four Hills, Mesa del Sol, South Valley, Westgate and the Southwest Mesa, Cedar Crest, Edgewood, Moriarty, Belen.