Scratching or scurrying inside a wall usually means rodents are moving through the cavity between the attic and the floors below. Both mice and rats do it, and the fix depends on which one you have.
Signs of mice in the walls
- Light scratching or scurrying behind drywall, often at night, when rodents are most active.
- Droppings about a quarter of an inch long and pointed (rat droppings are about half an inch with blunt ends). Look under sinks, behind the stove and fridge, in the garage and in pantry corners.
- Gnaw marks on boxes, food packaging, wood or wiring.
- Grease marks along baseboards where they run the same route every night.
- A musty or stale smell in a room, especially near a wall.
If the sounds are louder and mostly overhead, it may be rats in the attic instead. See rats in the attic and noises in the attic at night.
Why traps and poison alone don't solve it
- Mice need very little room to get in. A small gap is enough, so a home usually has several entry points, not one.
- If the entry points stay open, new mice replace the ones you catch.
- Poison can leave a dead rodent inside a wall where you can't reach it, and most anticoagulant rat poisons are now banned for home use in California. See the California rat poison ban.
What actually works
- Find every way in. A technician inspects the roofline, vents, crawlspace, garage and the lines where pipes and wires enter the house. See rodent inspection.
- Remove the mice inside. Done before sealing, so none are trapped in the walls.
- Seal the entry points. This is what stops the problem coming back. See rodent exclusion.
- Clean up. Droppings and soiled insulation are removed last.
What you can do today
- Store pantry food in sealed containers and don't leave pet food out overnight.
- Never sweep or vacuum droppings dry. Wet them with a disinfectant first and wear gloves.
- Write down where and when you hear or see signs. It helps the technician find the route.
Get it looked at
Tell us what you're hearing and we'll connect you with a state-registered pest control company that serves Los Angeles County. Start with mouse control, or call the number at the top of the page.
More guides
- A dead rat smell in the wall: what to do
- How rats get into your house, and where to look
- Rats chewing your car wires: what's going on
This guide is general information, not a substitute for an on-site inspection. SealWell is a referral service, not a contractor.
