How Mice Get Inside Your Home: Every Entry Point I Check on Every Job

Mice get inside through any gap larger than a dime — about 6-7 millimetres, or roughly the width of a pencil — because their skulls are the only rigid part of their body and everything else compresses to fit. Common entry points include foundation cracks, gaps around utility pipes, unsealed vents, worn door thresholds, and garage door corners. Sealing these is the only way to stop new mice from replacing the ones you've trapped.

Why a Dime-Sized Gap Is All It Takes

I've had homeowners argue with me about this until I show them the actual gap. A mouse doesn't need a hole — it needs a crack. Their collarbones are essentially vestigial, which lets them flatten their rib cage and squeeze through openings that look far too small to matter.

Mice can squeeze through cracks as small as a dime, while rats can enter through a quarter-sized hole. That's the benchmark I use on every inspection: if I can slide a dime into a gap along your foundation, siding, or utility line, that's a confirmed entry point, not a maybe.

The Foundation and Structural Gaps I Check First

Most infestations I trace back to the exterior envelope of the house, not the inside. On every job, I work the perimeter in this order:

• Foundation cracks and settling gaps — especially where poured concrete meets the sill plate or brick veneer
• Utility and pipe penetrations — the gaps left around water lines, gas lines, and electrical conduit where they pass through the exterior wall are rarely sealed properly at construction
• Dryer vents and exhaust vents — an unscreened vent is basically an open door
• Weep holes in brick veneer — these are supposed to be there for drainage, but they're an easy mouse entrance if not screened
• Garage door corners and thresholds — the rubber seal degrades within a few years and leaves gaps at both bottom corners

There are dozens of potential entry points in a home that rodents can sneak through, which is why a proper inspection covers the entire exterior, not just the spot where you found droppings.

Doors, Windows, and the Gaps You Live With Every Day

Interior clues matter too, but the doors and windows you use daily are frequently the weak point. Even the small gaps created by worn thresholds under doors will allow mice access to your home. I see this constantly on older Ontario homes where the original door sweep has compressed flat.

Things I check inside every home:

• Gaps under exterior doors (slide a flashlight test at night — if light shows, mice can get through)
• Window screens with tears or gaps at the frame
• Attic vents and soffit gaps, especially where squirrels or previous rodent activity widened an opening
• Gaps around AC line sets and exterior faucets
• Chimney caps — an uncapped chimney is an open invitation

Why Fall Is the Worst Season for New Entry

I get triple the call volume between late September and November. As outdoor temperatures drop, mice actively search for a heated structure to overwinter in, and a house that was mouse-free all summer can suddenly have activity within days. This is when I find the most new entry points being actively used, because mice test every gap along the foundation until one gives.

What Actually Stops Them (And What Doesn't)

Steel wool packed into a gap and finished with caulk or expanding foam is the standard I use — mice can chew through plastic, caulk alone, and even soft foam on its own, but they won't chew through steel wool. For larger gaps around pipes or vents, I use galvanized hardware cloth or copper mesh screwed into place, not just stuffed in.

Bait and traps deal with the mice already inside. They do nothing about the gap they came through. I've been called back to homes where a previous company set bait stations for months without ever sealing the actual entry point — the population just kept refreshing itself from outside.

Health Risks I Take Seriously on Every Job

This isn't just a property issue. Mice can contaminate food supplies with their droppings, urine, and saliva, which can transmit diseases such as hantavirus and salmonella, and they also chew on electrical wiring, insulation, and structural components, leading to potential fire hazards and costly repairs. That's why exclusion work isn't optional in my process — it's the core of the job.

Because of this, every product I use is Health Canada approved and safe to apply around kids and pets, and I explain exactly where I'm placing anything before I leave a home.

What I Do on an AstraHive Mouse Job

I've been doing this since AstraHive was founded in 2015, and the process hasn't changed because it works:

1. Full interior and exterior inspection to map every active and potential entry point
2. Identify the species and estimate population pressure from droppings, gnaw marks, and grease trails
3. Seal every confirmed entry point with steel wool, mesh, and sealant — not just the obvious one
4. Place bait and traps to eliminate mice already inside
5. Follow-up visit to confirm no new activity

Mouse jobs start at $300 CAD, with the final price depending on the size of the property and how many entry points need sealing. We offer same-day service across Durham, York, Peel, Simcoe County, and the wider GTA (75+ cities), and if mice come back after treatment, we re-treat at no charge under our 100% satisfaction guarantee. Call us at 905-925-8427 to book an inspection.

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 hole can a mouse fit through?

A mouse can squeeze through an opening as small as a dime, roughly 6-7 millimetres wide, because its skeleton compresses to fit through gaps larger than its skull. This is why sealing even tiny cracks along your foundation, siding, and utility lines matters as much as sealing an obvious hole.

Can mice get in through the garage?

Yes, garage doors are one of the most common entry points I find, especially at the bottom corners where the rubber seal has worn thin or compressed. A garage that connects to living space through an interior door gives mice a direct path into the rest of the home once they're inside.

Do I need to seal entry points if I'm already using bait or traps?

Yes, absolutely. Bait and traps only remove the mice currently inside your home, but if the entry point stays open, new mice will keep coming in from outside. Long-term elimination requires sealing every entry point, not just controlling the population you can see.

How many entry points does a typical house have?

On a typical inspection I find 3 to 6 active or previously used entry points on a single property, even when the homeowner only noticed one problem area. Common spots include foundation cracks, pipe penetrations, vents, and worn door thresholds.

Is it dangerous to clean up mouse droppings myself?

It can be, because inhaling dust from dried droppings or urine is a documented way people contract hantavirus. If you find a significant amount of droppings, ventilate the area, avoid sweeping or vacuuming dry debris, and consider having it handled professionally, especially in enclosed spaces like attics or crawl spaces.

Sources

• Health Canada — Mice can squeeze through cracks as small as a dime, while rats need only a quarter-sized hole, and worn door thresholds can also let mice in.
• Orkin Canada — There are dozens of potential entry points in a home that rodents can sneak through, requiring a full inspection of vulnerable pressure points.
• PestCheck — Mice can contaminate food with droppings, urine, and saliva, transmitting diseases such as hantavirus and salmonella, and can also chew wiring leading to fire hazards.

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.