Mouse Entry Points: The Exact Spots I Check on Every Ontario Inspection

A mouse can squeeze through any gap around 6-7 millimetres wide, roughly the diameter of a pencil, because its skeleton compresses everywhere except the skull. On every inspection I check foundation cracks, utility penetrations, dryer vents, garage door corners, exterior door thresholds and basement window frames first, since these are where gaps most often develop.

The Entry Points I Check First on Every Inspection

After years of inspecting homes across the GTA, Durham, York, Peel and Simcoe County, I see the same mouse entry points over and over. Mice don't need a large opening to get inside, and a gap the size of a dime is often all it takes.

I focus on where the exterior of the home meets the foundation, walls, doors, vents and utility penetrations. These junctions are where small gaps develop over time and where mice find a protected route indoors.

• Foundation cracks and openings: Small cracks, gaps around the foundation, and openings associated with brick veneer can provide access, particularly when they connect to a wall cavity or basement area.
• Utility and pipe penetrations: Gas lines, electrical conduit, cable lines and plumbing often pass through the foundation or exterior wall. Gaps around these become direct entry routes once the original sealant deteriorates or was never properly installed.
• Dryer vents and exhaust vents: Damaged, missing or improperly screened vent covers create openings into the exterior wall and give mice an easy route toward the interior.
• Garage door corners: Mice are thermotactic, meaning they naturally seek warmer, protected environments, and during cold weather they work toward the warmer corners of a garage door and chew through vulnerable edges.
• Exterior doors and thresholds: Gaps beneath or around exterior and garage-entry doors open up as weather stripping, thresholds or surrounding materials deteriorate.
• Basement windows and window wells: Older window frames and deteriorated surrounding materials create gaps that are easy to overlook from inside the house.
• Other exterior gaps and penetrations: I also check siding transitions, masonry joints and any spot where two different building materials meet.

Why Garage Door Corners Are a Common Mouse Entry Point

Garage doors deserve particular attention because mice aren't just looking for any opening, they're looking for a protected route toward warmth and shelter. As temperatures fall, they investigate the corners and edges of garage doors where small vulnerabilities exist.

Mice can also chew through materials that look like an effective barrier. That's why simply filling a vulnerable corner with soft foam or another chewable material rarely holds up as a long-term fix.

How I Seal Mouse Entry Points

Mouse exclusion isn't about filling every opening with the same material. The right approach depends on the size, location and type of opening, plus what the surrounding building materials are made of.

Depending on the situation, I use a combination of the following:

• Hardware cloth — a rigid mesh barrier for larger openings and vulnerable garage-door corners
• Copper mesh — packed into pipe and cable penetrations, then sealed
• Steel wool — used in combination with sealant on smaller irregular gaps
• Expanding foam and appropriate sealants — applied around or over rodent-resistant material, never alone on a gap a mouse can chew through

Larger openings usually need a physical mesh barrier, while smaller penetrations need a combination of rodent-resistant material and sealant so the gap can't be reopened. The objective isn't to make an opening look sealed. The objective is to create a barrier a mouse can't chew through, push aside or squeeze around.

Knowing Where Pest Control Ends and Structural Repair Begins

Not every opening I find is something a pest control company should repair. Sometimes mice are getting in because of an underlying structural problem such as significant foundation damage or deteriorated building materials that requires specialized construction work.

When I identify structural damage beyond the scope of exclusion work, I point it out to the homeowner directly and explain that it needs to be assessed and repaired by a qualified contractor. My job is to identify how the mice are getting in, address the entry points that fall within my scope, and clearly communicate when a larger structural repair is required. I don't cover up a problem that needs to be properly fixed.

Why Mice Don't Stop at the First Room

The ultimate goal for a mouse entering a home isn't the basement, garage or a wall cavity, it's a place that provides warmth, darkness, protection and access to food and water. That's why an attic can become an ideal destination: it's typically dark, quiet and insulated from outdoor temperatures.

Once mice reach the attic, they may establish nests and reproduce there, especially in a protected area with little human activity. A single infestation can escalate fast since mice can reproduce roughly every three weeks. From the attic, mice move through wall cavities and insulation spaces, eventually travelling between the attic, walls, basement, garage and living areas, turning what looked like a single-mouse problem into something much harder to control.

Mice are also a genuine health concern, not just a nuisance. Mice and rats are carriers of disease, and can damage property, and the deer mouse is the most common carrier of the deadly hantavirus, according to Health Canada. A peer-reviewed overview of the disease in Canada notes that personal risk reduction includes recognizing rodents or evidence of infestation and preventing rodents from entering the home in the first place, which is exactly why finding and sealing the original exterior entry points matters more than just removing the mice you can see.

What I See Most Often Across the Region

The exact entry points vary from property to property, but the underlying pattern is remarkably consistent. In Richmond Hill, Whitby, Pickering and communities throughout Durham and York Region, I regularly find mice exploiting small gaps around foundations, utility penetrations, vents, doors and garage areas.

Older homes carry years of settlement, deterioration and shrinking sealants that create new openings over time. Newer homes have their own vulnerabilities, particularly around utility penetrations and areas where exterior building materials meet.

Garage areas are especially important during colder weather. A mouse doesn't need a large damaged section of a garage door to gain access, a small vulnerable corner is enough for it to start working its way inside. That's why a proper mouse inspection is about more than looking for the hole where a homeowner saw a mouse — I look for the network of potential entry points that could allow rodents to repeatedly enter the property.

What This Costs and What's Included

Mouse control at AstraHive starts at $300 CAD, with final cost depending on property size. I've been running AstraHive since 2015, which puts us at 11 years of doing exclusion work across the GTA, Durham, York, Peel and Simcoe County. Every product I use is Health Canada approved and safe around kids and pets, and every job is backed by a 100% satisfaction guarantee, meaning I'll come back and re-treat at no charge if mice return within the covered period.

If you're hearing scratching in the walls or attic, or you've already spotted droppings, call 905-925-8427. We answer calls back within 5 minutes and offer same-day service across 75+ cities in the region.

Why Choose AstraHive

• Licensed & Insured: Certified by the Ontario Ministry of Environment, Conservation and Parks.
• Fast response: Same-day service available, with a callback within 5 minutes.
• 100% Satisfaction Guarantee: If pests come back, we re-treat at no additional charge.
• Proven track record: 5.0 stars on Google across 150+ reviews.
• Family & pet safe: Health Canada approved products on every job.

Frequently Asked Questions

How small of a gap can a mouse fit through?

A mouse can fit through a gap as small as 6-7 millimetres wide, about the diameter of a pencil or a dime. Their skull is the only rigid part of their body, so if the head fits, the rest of the body can compress to follow.

Why do mice keep coming back after I trap or remove them?

Trapping addresses the mice that are already inside, but if the original exterior entry points around the foundation, vents, utility lines or garage door aren't sealed, new mice can follow the same route in. Removing mice without exclusion work usually leads to repeat activity within weeks.

Are garage doors really a common mouse entry point?

Yes, garage door corners are one of the most common entry points I find, especially in colder months. Mice are thermotactic and seek warm, protected spaces, so they gravitate toward garage door edges and chew through vulnerable corners even if the door looks intact.

What materials actually stop mice from chewing back through a sealed gap?

Hardware cloth and copper mesh are the most chew-resistant materials, and I use them for garage corners, larger openings and pipe penetrations. Expanding foam or caulk alone isn't enough on its own since mice can chew through it, so foam and sealant are typically combined with a mesh barrier.

How much does mouse control cost with AstraHive?

Mouse control starts at $300 CAD, with the final price depending on the size of the property and the severity of the infestation. I determine the exact cost after a free, in-person inspection, and same-day service is available across the GTA, Durham, York, Peel and Simcoe County.

Sources

• Health Canada — Mice and rats are carriers of disease and can damage property, and the deer mouse is the most common carrier of hantavirus.
• PMC (Hantavirus pulmonary syndrome in Canada overview) — Personal risk reduction against hantavirus includes recognizing rodent infestation signs and preventing rodents from entering the home.

Areas We Serve

AstraHive Pest Control proudly serves 75+ communities across the following regions:

• Toronto: Toronto, North York, Scarborough, Etobicoke, East York, York, Leslieville, Lakeview
• Durham Region: Oshawa, Whitby, Ajax, Pickering, Clarington, Bowmanville, Courtice, Newcastle, Port Perry, Brooklin, Uxbridge, Scugog, Brock, Seaton
• York Region: Vaughan, Markham, Richmond Hill, Aurora, Newmarket, Thornhill, Woodbridge, Kleinburg, Maple, Stouffville, Unionville, Keswick, Holland Landing, East Gwillimbury, Georgina, King City, King Township, Nobleton, Berczy Village, Cathedraltown, Commerce Valley, Cornell, Wismer, Whitchurch-Stouffville, Sutton, Schomberg
• Peel Region: Mississauga, Brampton, Caledon, Malton, Port Credit, Streetsville, Meadowvale, Cooksville, Bolton, Palgrave
• Extended Service Area: Peterborough, Lindsay, Port Hope, Barrie, Bradford, Innisfil, Collingwood, Wasaga Beach, Orillia, Burlington, Oakville, Milton, Hamilton, Grimsby, St. Catharines, Welland, Niagara Falls

Don't see your city listed? Call us — we likely cover it.