Mice in Your Garage? A GTA Winter Guide

I have been doing pest control in the GTA long enough to know that the first mouse call of the season always comes in October. By November, the phones do not stop. Mice do not hibernate — when the temperature drops below about 10 degrees at night, they start moving towards heat sources. Your garage is the easiest entry point on most GTA homes, and from there it is a short trip through the wall voids into the kitchen.

Why Mice Love Your Garage

Think about it from the mouse's perspective. Your garage is:

Warmer than outside — even an unheated garage is 10 to 15 degrees warmer than a January night in Toronto.
Easy to enter — the gap under a standard garage door is often 6 to 10 millimetres. A mouse can squeeze through a gap the width of a pencil. That worn rubber seal at the bottom of the door? That is the front entrance.
Full of nesting material — cardboard boxes, stored insulation, old newspapers, fabric. Mice shred all of it for nesting.
Often has food — bird seed is the number one attractant I see in garages. Then pet food, grass seed, and garbage bins with loose lids.

Signs You Have Mice in the Garage

Mice are mostly nocturnal, so you will not always see them. But they leave plenty of evidence:

Droppings. Small, dark, rice-shaped pellets about 3 to 6 mm long. Check along the walls, in corners, and behind stored items. Fresh droppings are dark and soft. Old ones are dried out and grey.
Gnaw marks. Mice chew constantly to keep their teeth worn down. Look for tooth marks on cardboard boxes, plastic containers, electrical wiring, and the rubber seal of your garage door.
Shredded material. Finding bits of torn paper, fabric, or insulation behind boxes means someone is building a nest.
Urine smell. A musty, ammonia-like odour that gets stronger in enclosed areas. If you notice it when you open the garage in the morning, you have an active population.

What You Can Do Yourself

Before calling a pro, there are things you can do that actually help:

Fix the garage door seal. Install a new rubber weather strip along the bottom. If daylight is visible under the door when it is closed, mice are getting through.
Seal the gap where the gas line enters the house. This is entry point number one on most GTA homes. The gas line comes through the foundation wall, and builders almost never seal that penetration tightly. Pack steel wool into the gap and cover it with metal flashing or caulk. Mice cannot chew through steel wool.
Move food into sealed containers. Bird seed, grass seed, and pet food go into metal or glass containers with tight lids. Not plastic — mice chew through plastic overnight.
Get items off the floor. Store things on shelves. Switch from cardboard boxes to plastic bins. Mice nest in cardboard; they cannot nest in sealed plastic.
Keep the garage door closed at night. Sounds obvious, but I cannot count how many customers leave the garage cracked open for the cat.

When to Call a Professional

If you are finding fresh droppings every morning, hearing scratching inside the walls, or have actually seen a mouse in the house — not just the garage — it is time to call a licensed operator. Here is what a proper mouse exclusion job looks like:

Full inspection. The technician checks every potential entry point on the exterior — foundation cracks, pipe penetrations, soffit gaps, weep holes, dryer vents. A mouse can fit through any gap over 6 mm.
Strategic trapping. Snap traps placed along active runways inside the home and garage. Bait stations outside along the foundation. Glue traps are less common now — most licensed operators have moved away from them.
Exclusion sealing. Every entry point gets sealed with rodent-proof materials — steel wool and metal flashing for gaps, hardware cloth for vents, concrete patch for foundation cracks.
Follow-up visits. Usually two visits over 3 to 4 weeks to check traps, replace bait, and confirm the population is eliminated.

A full mice exclusion job on a typical GTA home — detached or semi — runs $350 to $600. The older the house, the more entry points, the higher the cost. A 1960s Scarborough bungalow with an original foundation will cost more than a 2015 Brampton build with a poured concrete basement.

Got mice in your garage or house? Get free quotes from licensed rodent control operators across the GTA.