If you hear light, quick scratching or scurrying in a wall at night or early morning, it is most likely house mice. They travel inside wall cavities between their nest and food, coming in at the bottom around pipes and the slab or at the top from the attic. You get them out by trapping where they exit the wall and sealing the gaps they use, rarely by opening the wall.
Here is how to confirm it and what to do.
What mice in walls sound like
Mice make light, fast sounds: scratching, skittering and sometimes faint squeaking or chewing. You hear them most at night and around dawn when the house is quiet. The noise moves up and down or across a wall.
Rats are heavier and louder, with thumping and running, and roof rats are usually in the ceiling or attic. Squirrels are active in daytime, mostly morning and late afternoon. The rodent noises at night article compares the sounds in more detail.
How mice get into walls
It depends on how the house is built.
Concrete block homes, common across Arlington, the Westside and much of the Southside, have a narrow space between the block and the interior drywall. Mice get into it through weep holes, gaps around hose bibs and line penetrations, and from the attic down along wires.
Wood-frame homes on slabs, typical of newer neighborhoods, have open stud cavities. Mice come in from the garage, from the attic along plumbing vents and wiring, and through gaps where pipes come up through the slab under sinks.
Raised wood-frame homes in Springfield, Riverside and Murray Hill let mice climb up from the crawl space through gaps in the subfloor around pipes.
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(904) 593-1371Tap to callOther signs to look for
Check the places where wall cavities open into rooms:
- Under kitchen and bathroom sinks, where pipes come through the wall or floor
- Behind the stove, fridge and dishwasher
- Inside lower cabinets, especially the back corners
- Along baseboards in the noisy room
- In the attic directly above the wall, where wires and pipes drop down
Droppings 1/8 to 1/4 inch long, gnawed edges on cabinet backs and bits of insulation or paper are good signs you have found an exit.
Getting them out
Set snap traps at the exits: under the sink next to the pipe hole, behind appliances, inside the cabinet next to the gap. Set them perpendicular to the wall with the trigger toward the wall, per the University of Kentucky. Bait with peanut butter.
Don't put poison bait in or near walls. Mice that eat it often die inside the wall, and the smell in a Jacksonville summer can last for weeks. See dead rodent removal if that has already happened.
After a few days of catches, seal the interior gaps with copper mesh and sealant, then seal the outside entries. Extension guidance on rodent exclusion says mice can get through openings larger than 1/4 inch.
Shared walls
In townhomes, condos and apartments, the mice in your wall may live next door. Sealing your side helps, but if neighbors aren't treating, mice keep coming. Tell your landlord or association in writing. In most Florida rentals other than single-family homes and duplexes, Statute 83.51 puts reasonable provisions for rat and mouse extermination on the landlord. See the tenant and landlord guide.
If you smell something in the wall
A sharp, rotten smell from one wall a few days after the noise stops usually means a mouse died inside. It happens most often when someone has used poison bait, but it can happen with traps too if a mouse is injured.
In a Jacksonville summer, the smell gets strong fast. Flies near an outlet, light switch or baseboard are a good pointer to the spot. Before cutting anything, check under cabinets, behind appliances and in the attic above the wall, since the carcass is sometimes reachable.
If a small opening is needed, cut it low on the wall where it is easy to patch, or behind an appliance where it won't show. Wear gloves, spray the carcass with disinfectant before removal and double-bag it. See dead rodent removal if you'd rather have someone find it.
When to bring in a technician
Call if the noise continues after a week or two of trapping, if you hear it in several walls, if you smell something dead, or if you can't find where they are getting in. A technician can trace the runways, set traps in the attic and crawl space, and seal entry points you might not reach. See mice in walls removal.
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(904) 593-1371Tap to callCommon questions
Will mice in my walls go away on their own?
Not usually. As long as there is food nearby and a way in, they stay. Trapping at the exits and sealing gaps is what works.
Do I need to cut a hole in the wall?
Rarely. Traps at the exits and sealing the entries usually solve it. A small opening may be needed to remove a dead mouse.
Can mice in walls chew electrical wires?
Yes. Rodents gnaw constantly, and wires in walls are within reach.
Why do I only hear them at night?
Mice are most active at night and early morning, and the house is quieter then.