Most Milton homeowners ask the wrong first question. It is not "how do I get rid of these mice?" — it is "how do mice get in house after house on this street, including mine?" A mouse needs a dime-sized gap, and almost every house has several. Traps and bait deal with the mice inside; the audit — finding every gap, foundation to roofline — stops the next ones.
The dime test: how small a gap is a doorway
Health Canada puts it plainly: mice can squeeze through cracks as small as a dime — about a quarter inch, roughly 6 mm. A gap the width of a pencil is a door until proven otherwise.
Three abilities turn a tiny flaw into a door:
They squeeze. A mouse’s body compresses through openings that look far too small for it.
They gnaw to widen. A mouse's front teeth grow continuously, so it chews to keep them worn down — and a crack that is almost big enough today can be chewed into a doorway. Mice chew through foam, rubber, vinyl, wood and plastic, so a hole that looks filled can still be open to them.
They climb. House mice are excellent climbers that can run up rough vertical surfaces — brick, wood and concrete included. The roofline counts as much as the foundation.
They find gaps the way you feel a draft: warm air and food smells leak out through a house's openings, and a mouse follows that air straight to the hole.
Why Milton homes give the audit so much to find
Milton puts three kinds of mouse pressure on one map. Older downtown homes have had decades to settle — foundations shift, caulking ages, and small cracks open a fraction at a time. Newer subdivisions went up beside fields and farmland, and a house still settling opens gaps of its own. And across town, homes back onto green space, creek land and the escarpment — the field and woodland edges mice live in all summer.
When the nights turn cold, those mice move toward warmth, food and a quiet place to nest. Health Canada notes that deer mice commonly move into buildings near fields and woodlands in the fall, and house mice need even less encouragement. That is mice removal season in Milton — the houses that get hit are the ones with a dime-sized gap nobody has looked for.
The entry-point audit: foundation to roofline, in order
An audit is a slow walk, not a glance. Start low, finish high, and check every place two materials meet or a pipe or wire passes through the wall:
Foundation cracks and holes — walk the whole perimeter at ground level, including behind shrubs and items stored against the wall. Patching foundation cracks is one of Health Canada's own starting points.
Where the siding meets the foundation — one of the most overlooked joints on the house, and a straight run into the wall.
Utility penetrations — every water pipe, gas line, cable and air-conditioning line through the foundation or a wall. The hole was cut for the line, not sealed for the house, and old sealant cracks.
Doors and the garage — check for daylight under exterior doors and a worn threshold; even that small gap is enough. Then the bottom corners of the garage door, and the door from the garage into the house.
Weep holes in brick — the small drainage openings at the base of a brick wall. Never caulk or foam them shut: the wall needs them to drain. They need a proper insert or screen that lets water through but keeps mice out.
Vents and the roofline — vents are open by design, so they need screening mice cannot chew through. Finish at the soffit corners and the gaps where the roof meets the walls. Ontario's guidance on preventing and managing conflicts with small animals starts in this same place: seal the entry points, carefully, so no animal is sealed inside.
Reading the sign: is that gap actually in use?
Not every gap is an active door, and the mice tell you which ones are. Look for droppings — small, dark, about 3 to 6 mm long, like grains of rice — near a gap, fresh gnaw marks at its edge, and light scratching in walls after dark. One gap with sign outranks ten with none — but the audit records all of them, because a mouse turned away from a sealed door tests the next gap.
Sealing it shut: the materials that actually hold
Closing the doors only works with materials mice cannot chew:
Around pipes and cables: steel wool packed tightly in before sealing over — the fix Health Canada recommends — so a mouse hits metal first.
Vents and larger openings: fine mesh metal screening, fastened so it cannot be pushed aside.
Foundation cracks: a cement or mortar patch, not a soft filler.
Under doors: metal weather stripping and a sound sweep or threshold.
Spray foam alone is not a seal — mice chew straight through it. Baiting alone never finishes the job either: Health Canada says baits and poisons should not be the only method used, and removing easy entry points is the first line of defence. Bait closes no holes — the next mouse uses the same door. And openings are closed as part of a removal plan, never sealed on the spot with mice still inside — that locks the problem in the walls instead of ending it.
Mice removal in Milton: how Regional Wildlife Services runs the audit
On wildlife removal in Milton calls, Sean Thornton — owner-operator, 20+ years removing wildlife humanely — does the work himself:
Audit inside and out. Attic, basement, kitchen and garage for sign; the full exterior — foundation, utilities, garage, siding, weep holes and roofline — for every gap.
Read the sign before naming the job. Droppings, gnaw marks and timing separate mice from squirrels and raccoons, so the fix matches the animal.
Seal the home permanently. Every entry point closed with materials mice cannot chew through, and vents screened as part of the exclusion work — no poison program, no monthly top-up.
Advise honestly on cleanup. Never sweep or vacuum dry droppings. Soak them with disinfectant first, wear gloves, and bag what you pick up; a heavily fouled space gets assessed first.
Frequently asked questions
How do mice get in a house that looks sealed?
Through a gap you have walked past a hundred times — around a gas line, under a worn threshold, at a garage corner, or up the brick to a soffit gap. A mouse only needs one dime-sized one.
I filled the hole with spray foam. Why are they back?
Because foam is not a barrier — mice chew through foam, rubber, vinyl, wood and plastic. A lasting seal puts metal in the gap: steel wool around pipes, metal mesh over openings, mortar in cracks.
Can mice really climb to the roofline?
Yes. House mice climb rough surfaces — brick, wood, concrete — and travel along wires and branches. That is why a proper audit finishes at the roofline.
Should I seal a gap the moment I find it?
Not on its own. If mice are still using it, sealing it alone can lock the problem inside the walls. Entry points are closed as part of a removal plan, in the right order.
Why not just keep traps and bait stations going?
They deal with the mice inside today and close none of the gaps they used. As long as one dime-sized door stays open, new mice follow the same route in.
Found droppings in a Milton home — or hearing scratching after dark?
Call Regional Wildlife Services at 905-320-8984, or reach us through the contact page. You will get a named owner-operator with 20+ years removing wildlife humanely — a full entry-point audit from foundation to roofline, and every gap sealed with materials mice cannot chew through. Phone calls and bookings are taken 7 days a week; service appointments run Monday to Friday typically. Serving Burlington, Oakville, Milton, Hamilton, Stoney Creek and Niagara — call 905-320-8984.
