You probably don’t think much about what’s happening behind your walls in January, but the animals outside sure do. When temperatures drop and snow piles up, warm homes across Canada become prime real estate for small winter invaders.

At Skedaddle Humane Wildlife Control in Ajax, we see it every year. Canadian winter mouse infestations spike during the coldest months because these small animals can squeeze through gaps you wouldn’t believe. If you’ve ever wondered how mice entry points in the winter — or how to stop them, you’re about to find out.

By the time you notice droppings or faint scratching, the problem is usually well underway. You might not realize it, but those tiny guests have already found their way through cracks, vents, and gaps all over your home. Let’s walk through how mice sneak into Canadian homes during deep winter, and what we do to keep them out for good.

Foundation Cracks Let the Cold and Mice In

When you think of entry points, you might look up toward the roof. But in most homes, the problem starts low. Small cracks in your foundation can act like open doors during winter.

As temperatures change, concrete expands and contracts. Even a gap the size of a dime is large enough for a mouse to slip through. Once inside, they move up through wall voids and insulation until they reach the warm attic.

That’s why sealing these cracks professionally is one of the most important ways to prevent mice in winter.

Gaps Around Utility Lines and Pipes

Where your gas line, air conditioner tubing, or water pipes enter the house, there’s often a little space left open. These are some of the most common mice entry points in the winter.

We often find them in:

• Basement walls and laundry rooms
• Behind kitchen cabinets
• Around furnace vents or dryer exhausts
• Near outdoor faucets or hose bibs

To a mouse, those gaps feel like tunnels leading to warmth and food. Once they squeeze in, they rarely leave on their own.

Broken Door Sweeps and Garage Seals

You might not notice how much heat escapes from under your door, but animals can. A worn-out door sweep or cracked garage seal gives easy access.

Garages, in particular, are a favourite starting point. From there, it’s just a short climb up to wall cavities or ceiling insulation. The warmth from vehicles, heaters, or stored food makes garages even more appealing in deep winter.

Unsealed Attic Vents

Your attic vents help your home breathe, but they can also invite uninvited guests. Mice climb siding, gutters, or nearby vines to reach vents that have loose screens.

We often see this during attic inspections:

• Torn or rusted vent screens
• Cracked caulking around vents
• Missing mesh covers on roofline vents

Replacing these with durable materials is a key step in Canadian winter mouse infestations prevention and it’s something we handle as part of our sealing process.

Gaps Under Siding and Trim

When siding pulls away from your home or trim starts to warp from frost, small gaps appear; the perfect size for entry.

Mice love to follow the edges of walls, especially where siding meets the foundation or roofline. These hidden gaps lead straight into walls or attics.

Our team uses specialized sealants and flashing that blend into your exterior while keeping the structure airtight. That means no entry for animals and less heat loss for you.

Roofline Openings Created by Ice Damage

Heavy snow and ice buildup can pull roof edges apart, creating gaps under shingles and eaves. Once that happens, small animals can squeeze right in.

Typical signs include:

• Chewed insulation near roof edges
• Scratching noises at night
• Bits of shredded material near soffits or gutters

Fixing these weak spots helps stop both heat loss and future mice entry points in the winter.

Dryer and Furnace Exhausts

These vents blow out warm air and that warmth attracts attention fast. When vent covers crack, come loose, or lose their screens, it’s an open invitation.

We often find nests built right inside the vent tubing. It’s risky because nesting materials can block airflow and increase fire hazards. Our team uses chew-proof, mesh-style covers that maintain ventilation while keeping animals out.

Window Wells and Basement Windows

Even if your basement windows are sealed, the surrounding well might not be. When snow piles up, animals use it as a ramp straight to the window frame.

Over time, moisture weakens seals and small gaps form. Once inside, mice travel freely through insulation or ducts. Checking these areas in winter is one of the easiest prevent mice in winter habits to remember and one our team focuses on during inspections.

Poorly Fitted Chimney Caps

Your chimney might seem too high for mice to reach, but that doesn’t stop them. These determined climbers can scale rough brick or vines. If a chimney cap is missing or rusted, they’ll slip inside.

From there, they can drop into the smoke shelf or crawl through adjoining walls. We install secure metal caps that let your fireplace vent properly while blocking unwanted guests.

Cracked Window Frames and Doors

Cold weather causes wood to shrink and expand, leaving gaps you can’t always see. Mice can detect warm air and use those tiny openings to enter.

Even a loose window latch or worn weatherstripping can be enough. You might not feel the draft, but they will. Our team checks these details during every assessment because sealing them helps both pest prevention and energy efficiency.

Openings Around Decks and Porches

Many homeowners overlook decks and porches, but they’re common hiding spots. When snow builds up around the base, animals tunnel beneath and find small cracks leading into the home.

We’ve seen this hundreds of times in Canadian neighbourhoods. The area under the deck stays warm and protected, giving perfect cover to explore nearby wall gaps. Sealing or reinforcing this space removes one of the most popular routes inside.

Roof Intersections and Gable Joints

Where two rooflines meet, you often find small seams or joints that expand in cold weather. These weak points allow entry right into attic insulation.

During deep winter inspections, we focus on these areas because they’re hidden but critical. Mice can slip in unnoticed and stay active for months before you hear them.

Open Wall Cavities Around Plumbing

Behind sinks, around bathtubs, or under dishwashers, there are often open spaces where pipes run through walls. These cavities connect directly to basements or crawl spaces — and act like hallways for small animals.

Our technicians identify these areas and seal them safely from inside without blocking access to plumbing or vents.

Ventilated Soffits and Eaves

These parts of your roofline often contain small vents designed to prevent moisture. Unfortunately, over time, they weaken and provide easy access.

You might notice droppings or insulation bits falling from the eaves, both signs that something’s already inside. Using chew-resistant screening is one of our key methods for closing these entry points permanently.

Winter Mice Prevention With Our Professionals

You don’t have to handle any of this on your own. Our professionals at Skedaddle Humane Wildlife Control specialize in long-term protection, not quick fixes.

Here’s what we do to stop Canadian winter mouse infestations safely and humanely:

• Inspect every inch of your home for weak spots and openings
• Use one-way doors to let animals exit without harm
• Seal and reinforce every potential mice entry point in winter
• Replace or clean affected insulation
• Prevent future infestations with durable, weatherproof materials

We handle the full process so you don’t have to touch or clean anything. It’s fast, safe, and completely humane.

Stay Ahead of Winter Infestations

The truth is, mice entry points in the winter can appear anywhere, from your foundation to your roofline. Cold weather pushes them inside, and once they find warmth, they won’t leave easily.

At Skedaddle Humane Wildlife Control in Ajax, we’ve helped thousands of homeowners stop Canadian winter mouse infestations before they worsen. Our team combines careful inspection, humane removal, and durable sealing to protect homes all season long.

If you hear scratching, see droppings, or suspect activity in your walls, don’t wait. Request an estimate to learn more about how we can help you prevent mice in winter and keep your home safe and warm through the coldest months.