How Mice Get Into GTA Homes: Every Entry Point Explained
By PestRecord Editorial Team
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A mouse can squeeze through a gap the width of a dime. That is not a metaphor. It is a fact of physics that keeps pest control operators busy every winter in the GTA. Mice are the number one rodent complaint in our region, and the solution is not more traps. It is better sealing. Here is every entry point you need to check on your GTA home.
The 6mm Rule
A mouse can fit through any opening larger than 6 mm (about a quarter inch). A standard pencil is 7.5 mm. A dime is 17.9 mm. That means if you can see daylight around a pipe, a mouse can fit through it.
This is the most important number to remember when inspecting your home.
The Most Common Entry Points
1. Gas Line Penetration
The gas line enters your home through the foundation wall, usually in the basement.Builders rarely seal this properly. Look for the gap around the pipe where it enters. This is entry point number one on most GTA homes.
2. Garage Door Seals
A garage door seal that has worn down over the summer leaves a gap. Mice can also squeeze through gaps in the garage door tracks and panels. Inspect the rubber weather stripping and replace if cracked or missing.
3. Brick and Foundation Junction
Where the brick meets the foundation, there is a natural gap. Over time, mortar degrades and mice squeeze through. This is especially common on older GTA homes in neighbourhoods like the Annex and Leslieville.
4. Window and Door Frames
Gaps around window frames and under door frames are common entry points. Check the corners where the frame meets the siding or brick. Mice can also enter through gaps in the weather stripping under doors.
5. Soffit Gaps
Soffits (the underside of your roof eaves) can develop gaps where they meet the wall. These are high entry points that lead directly into the attic. Birds and squirrels can also use these gaps.
6. Exterior Vents
Dryer vents, range hood vents, and bathroom vents that lead outside can have gaps in their housing or where they meet the siding. Check that vent covers are intact and securely attached.
7. Foundation Cracks
Even small foundation cracks can be mouse entry points. Any crack wider than a credit card (about 1 mm) can be widened by water freeze-thaw cycles and become large enough for mice.
8. Pipe and Wire Penetrations
Any place a pipe or wire enters the house creates a potential entry point. Water lines, electrical conduit, cable lines, and telephone wires all create gaps that mice can use.
When to Seal
Timing matters. August through September is the ideal time for exclusion work. By then, the weather is still warm enough to work outside and mice have not yet started moving indoors in large numbers. By October, mice are already looking for warm shelter and may get inside before you finish sealing.
If you wait until November or December, you may trap mice inside when you seal the last gap. Always inspect and seal entry points before setting traps.
Materials to Use
- Steel wool. Mice cannot chew through it. Pack it into gaps and cover with metal flashing or caulk.
- Hardware cloth. 1/4 inch mesh for vents and larger gaps.
- Metal flashing. For covering patched gaps.
- Silicone caulk. For smaller gaps and cracks.
- Concrete patch. For foundation cracks.
What NOT to Use
- Steel wool alone. Without a covering, mice can pull it out.
- Plastic or vinyl. Mice chew through these.
- Papier-mache or cloth. Mice chew through anything soft.
- Expanding foam alone. Mice chew right through it. Use foam with steel wool underneath.
Professional Exclusion
A professional mouse exclusion job includes:
- Full exterior inspection of all potential entry points
- Sealing every gap over 6 mm with proper materials
- Strategic trap placement
- Follow-up inspection
Expect $350 to $600 for a typical GTA home.
Frequently Asked Questions
How small of a gap can a mouse fit through?
A mouse can fit through any gap larger than 6 mm (the width of a dime).
What is the most common mouse entry point in GTA homes?
The gas line penetration where it enters the foundation is the number one entry point.
When do mice start entering GTA homes?
Mice start looking for shelter in late August and early September.
Should I trap or seal first?
Always seal first. Trapping without exclusion means new mice will find the same opening.
How much does mouse exclusion cost in the GTA?
Professional mouse exclusion runs $350 to $600 for a typical GTA home.
Ready to mouse-proof your GTA home? Get free quotes from licensed mouse control operators today.