Mice move indoors in fall ahead of the cold, and a Worcester home with open gaps gets the same visit every year. A house mouse needs a gap the width of a pencil, and the gaps are usually where utility lines enter, where the garage door meets the frame, and where the foundation meets the sill. Winter is when the mice are already inside — the work that keeps them out happens in fall, before the cold arrives.
The plan has three parts, in order: seal the entries, remove the food at the wall, and trap on the runs for the mice already inside. Sealing is the half that lasts. Trapping without sealing is a subscription to the same problem, and food at the wall draws new mice to the gaps faster than traps can remove them.
TL;DR
Problem: mice move indoors in fall through pencil-width gaps, and stay all winter.
Solution: seal the entries, remove the food at the wall, and trap on the runs.
When to call: in fall, before the cold — or the moment you hear scratching in the walls.
Seal the gaps before the cold
Walk the foundation in fall and look for the gaps mice use: where the gas and water lines enter, where the garage door meets the frame, where the foundation meets the sill, and where vents have lifted. A mouse passes through a gap the width of a pencil, so the list is detailed. Seal with materials mice cannot chew through — foam and soft wood are chewed through in a night, so the sealing uses metal mesh, cement, and hardware cloth where the gap is large.
Remove the food at the wall
A pet bowl left out overnight feeds the mice the traps are trying to remove. Bird seed spilling by the foundation draws mice to the wall every evening. Open pantry bags feed the population inside. The food list is worked through alongside the sealing: pet bowls come in at night, pantry food goes into sealed containers, bird feeders move away from the foundation, and the compost pile moves away from the house wall.
Trap on the runs
Traps go onto the runs mice use — along wall lines, behind appliances, in the attic runs — placed where the droppings are thickest, not where they are convenient. Mice travel along edges and avoid open space, so a trap in the middle of a room catches dust. Follow-up visits check whether the traps are still catching and whether new signs appear.
Winter inside: what to watch for
Once winter sets in, the signs to watch for are droppings behind the stove and along the basement wall, gnaw marks on pantry bags, and scratching in the walls at night. A mouse inside in winter is running a route to food, and the droppings cluster along that route. The visit follows the droppings to the run, and the run to the entry that was missed in fall.
Steps
Walk the foundation in fall
Look for gaps where utility lines enter, at garage door corners, and where the foundation meets the sill. List every gap.
Seal with chew-proof materials
Use metal mesh, cement, and hardware cloth. Foam and soft wood are chewed through in a night.
Move the food
Pet bowls come in at night, pantry food goes into sealed containers, bird feeders move away from the foundation.
Trap on the runs
Place traps along wall lines and behind appliances, where the droppings are thickest. Check them over weeks, not days.