How do I keep mice and rats out of my Ottawa garage when it gets cold in the fall?

Rodent-proofing is genuinely one of the most practical things you can do for your Ottawa garage before winter, and the good news is that most of it is straightforward work a homeowner can handle. The core principle is simple: mice can squeeze through a gap the size of a dime, and rats through a gap the size of a quarter, so your job is to find and seal every opening before the cold drives them indoors in October and November.

Start with the garage door itself, because that bottom seal is almost always the weakest point. Ottawa's freeze-thaw cycles and road salt abuse wear out bottom seals quickly — if yours is cracked, brittle, or doesn't make full contact with the floor when the door is closed, replace it. This is an easy DIY job: bottom seals are available at any Ottawa home improvement store and attach with a simple retainer channel. While you're at it, check the side and top weatherstripping for gaps. A flashlight test on a bright day — close the door and look for light coming through — will reveal every problem spot quickly.

Next, walk the entire perimeter of your garage looking for gaps where the wall meets the foundation, around any pipe penetrations, conduit entries, utility lines, and where the garage door frame meets the wall. Steel wool stuffed into gaps and sealed with caulk or expanding foam is effective for small openings — rodents won't chew through steel wool the way they will through foam alone. For larger gaps, galvanized hardware cloth (quarter-inch mesh) cut to size and screwed over the opening is the durable solution.

Check your soffit and roof vents if your garage has them, because mice are excellent climbers and will enter from above just as readily as from ground level. Vents should have intact mesh screens — replace any that are rusted out or missing. If your garage has a door into the house, make sure the door sweep is in good condition and the door closes tightly with no daylight visible around the frame.

Inside the garage, eliminate what attracts rodents in the first place. Birdseed, grass seed, pet food, and any grain-based products stored in cardboard boxes or bags are an open invitation. Transfer these to sealed metal or heavy plastic containers. Clutter — especially cardboard boxes stacked on the floor — provides ideal nesting habitat. Getting items up off the floor onto shelving makes your garage far less hospitable.

One honest note: if you already have an active infestation, sealing entry points traps them inside, which creates its own problem. Deal with any existing population first using snap traps (more humane and effective than glue traps), then seal the entry points once activity has stopped. The timing matters — ideally complete your rodent-proofing in September before the fall migration pressure begins, because once temperatures drop below about 5 degrees Celsius, every mouse in your neighbourhood starts looking for warm shelter.