· by Michael Blair, Nashville's Pest Control
Mice come indoors as temperatures drop, and Middle Tennessee houses give them plenty of routes. Trapping deals with the individuals present; exclusion is what stops the next ones.
How little space they need
A mouse fits through a gap around a quarter of an inch — roughly a pencil. Rats need about half an inch. Anything you can push a pencil into is an entry point.
They also climb well and gnaw soft materials, so a small gap becomes a larger one.
Where they get in here
The crawl space access door, gaps at the rim joist, around pipe and wire penetrations, behind dryer vents, under garage doors with a worn seal, and where the siding meets the foundation.
In older Nashville houses, gaps around plumbing under kitchen and bathroom cabinets are a frequent internal route from the crawl space.
- Crawl space access and vents
- Rim joist and sill plate gaps
- Pipe, wire and duct penetrations
- Worn garage door bottom seal
- Gaps under sinks connecting to the crawl
Sealing properly
Copper mesh or stainless wool packed into gaps and then sealed works, because they cannot gnaw through it. Expanding foam alone does not — they chew straight through.
Hardware cloth over larger openings and vents, fastened rather than pushed in.
Trapping alongside
Snap traps set perpendicular to walls with the trigger toward the wall, in the runs where droppings appear. Mice travel along edges rather than across open floor.
Bait sparingly — a small smear works better than a large lump, which they can take without setting it off.