How to Keep Mice, Wasps & Pests Out of Your Garage: Sealing the Gaps Around Your Door

The Biggest Door on Your House Is Also the Easiest Way In

Your garage is the one part of the home most of us never quite finish sealing up. It has the largest opening on the whole house, a door that moves up and down thousands of times a year, a floor that meets the driveway at grade, and more often than not, shelves of bird seed, pet food, recycling and cardboard that read like a welcome sign to a mouse. Put those together and it is no surprise the garage is where most homeowners first notice droppings, a wasp nest, or a chewed bag of grass seed.

The reassuring part is that the garage door itself is one of the most controllable entry points you have. A worn bottom seal or a half-inch gap at the corner is an open invitation; a door that seals cleanly to the floor and the frame closes that invitation off. This guide explains why pests target the garage, the specific gaps around a garage door that let them in, the seals that shut them out, and a simple, accurate prevention routine you can run yourself. Every external link in this article was verified live the morning it was published.

Why Pests Love the Garage in the First Place

Mice, rats, wasps and insects are not looking for trouble; they are looking for the same three things every living creature needs: shelter, food and water. A typical Canadian garage offers all three in abundance, especially heading into the colder months when outdoor food gets scarce and a heated or even an unheated-but-sheltered garage starts to look like prime real estate.

Health Canada is blunt about what draws rodents in. In its guidance on rats and mice, it lists the cosy nesting sites in unused clutter around the house and garage, accessible food, and standing water as the main attractants. The garage tends to have all of them at once: stacked boxes and old furniture for nesting, bags of pet food or birdseed for feeding, and a slow drip from a tap, a fridge, or a sweating pipe for water.

Wasps are after something a little different. As Health Canada notes in its page on wasps, social wasps look for sheltered spots to build their paper nests and are drawn to both protein and sweet food, which is why an open recycling bin of pop cans in a quiet garage corner is so appealing. Spiders, cluster flies, earwigs and ladybugs simply follow the warmth and the smaller insects already inside.

The Gaps Around a Garage Door That Let Them In

Here is the single most useful fact in this entire article, and it comes straight from Health Canada: a mouse can squeeze through a crack as small as a dime, while a rat can get through a hole the size of a quarter. Health Canada specifically warns that "even the small gaps created by worn thresholds under doors will allow mice access to your home." In other words, the gap does not have to look like a problem to you. If you can see daylight under or beside your closed garage door, a mouse can already see an opportunity.

On a garage door, those gaps tend to show up in five predictable places:

• Under the door (the bottom seal). The flexible strip along the bottom of the door is the first thing to wear out. Cold makes it stiff and brittle, sun and ozone crack it, and an uneven floor leaves gaps even when the seal looks intact. This is the number-one rodent entry point on most garages.
• Where the floor meets the driveway (the threshold). Many slabs are not perfectly flat. A low spot in the middle or a dip at one corner can leave a channel a mouse can walk straight through, even with a healthy bottom seal.
• Down the sides and across the top (the jamb seals). The weatherstripping that runs up the door frame and across the header keeps wind, rain and insects out of the perimeter. When it shrinks, curls or was never installed, it leaves a continuous vertical gap.
• The bottom corners. Even a well-sealed door often leaves small triangular openings at the two bottom corners where the bottom seal and the side seals meet. These corners are a classic mouse highway.
• Gaps in the wall around the opening. Cracks in the foundation, unsealed gaps where the framing meets the block, and open service penetrations for wiring or pipes all sit close to the door and are easy for pests to find.

If you want a fast self-check, do it at night. Close the garage door, turn off the garage lights, and have someone shine a bright flashlight along the bottom and up the sides from the outside. Any light you can see from inside is a gap, and any gap is a potential entry point.

Step 1: Seal the Bottom of the Door

Because the bottom seal is both the most common entry point and the easiest to fix, it is where almost every pest-proofing project should start. A fresh, flexible bottom seal that presses evenly against the floor along the entire width of the door shuts out mice, insects, drafts, water and blowing snow in one move.

Replacing a worn bottom seal is one of the most satisfying do-it-yourself jobs on a garage door, and it usually costs under sixty dollars in parts. Our garage door bottom seal replacement guide walks through how to identify your seal type, the retainer styles, and the safe step-by-step procedure for swapping a worn T-style or nailed-on seal. The key point for pest control is fit: even a brand-new seal will not keep a mouse out if the floor underneath it dips, which is exactly where the next step comes in.

Step 2: Close the Floor Gap With a Threshold Seal

When the concrete itself is uneven, the bottom seal cannot do the job alone, no matter how new it is. A garage door threshold seal solves this from the other direction. Instead of hanging from the door, it bonds to the floor and rises to meet the door, sealing the low spots a bottom seal bridges over. It is one of the most effective ways to stop water, snow and pests where the bottom seal cannot.

A threshold seal is not always the right tool, though, and installing one over a garage that already has a drainage problem can trap water inside. Before you commit, read our garage door threshold seal guide, which covers the drainage check every Ontario garage needs first, when a threshold is the right fix versus the wrong one, the step-by-step install, and the winter cautions specific to our climate. Used in combination, a good bottom seal and a threshold seal close the entire floor line.

Step 3: Seal the Sides and Top of the Door

With the floor handled, turn to the perimeter. The jamb seals, sometimes called stop moulding or perimeter weatherstripping, run up both sides of the door and across the top. When they are missing, shrunken or curling away from the door, they leave a continuous gap that insects, drafts and small rodents exploit, and they are one of the most commonly overlooked parts of the whole door.

Replacing jamb seals is a manageable do-it-yourself project, and our garage door jamb seals guide covers the three common seal types, how to measure and install them, and the energy savings of a tight perimeter in a Canadian winter. Pay particular attention to the two bottom corners where the side seals meet the bottom seal; that junction is where many otherwise well-sealed doors still let mice slip in, and a properly fitted side seal that reaches all the way to the floor is what closes it. For the full picture of how all of these seals work together, our complete garage door seal guide ties the bottom, threshold and perimeter systems together.

Step 4: Make the Garage Itself Less Appealing

Sealing the gaps is the structural half of the job. The behavioural half is removing the food, water and shelter that drew pests to the door in the first place. Even a perfectly sealed garage will keep tempting fate if the inside smells like an open buffet. Health Canada's rodent prevention guidance is clear that rodent-proofing and good sanitation have to work together, and the same logic applies to insects.

The highest-value habits for a Canadian garage are straightforward:

• Store all food in sealed metal or glass containers. This is the big one. Pet food, birdseed, grass seed and fertilizer in their original paper or plastic bags are mouse magnets. Health Canada specifically recommends storing dry food and dry pet food in metal or glass containers, which cardboard and soft plastic cannot match.
• Cut the clutter. Stacks of cardboard, old furniture and bins of soft material are ideal nesting sites. Switch to sealed plastic totes, keep them off the floor where you can, and clear the corners. Our garage door and garage cleaning guide includes a practical decluttering routine.
• Eliminate standing water. Fix dripping taps, dry up condensation, and do not leave pet water bowls out overnight. A pest needs a drink as much as a meal.
• Manage the recycling and garbage. Keep cans rinsed and bins covered with tight-fitting lids. This is what keeps wasps from treating your recycling corner as a feeding station all summer.
• Keep the outside edge clear. Cut grass and weeds back from the garage wall, and keep firewood raised about 30 centimetres off the ground and away from the building, exactly as Health Canada advises. A clear, dry perimeter gives rodents nowhere to stage from.

Summer brings its own version of this checklist, since wasps and mice are most active in the warm months. Our summer garage door care guide folds pest prevention into the wider seasonal routine.

Don't Forget Moisture: A Damp Garage Is a Pest Magnet

Water deserves its own mention because it is so often overlooked. A garage that sweats in winter or stays humid in summer offers pests the one resource that is hardest to find elsewhere, and persistent dampness also feeds the mould and softens the cardboard that make a space attractive to nest in. If your door or walls show condensation, droplets or frost, that moisture is part of your pest problem. Our garage door condensation guide explains why it forms and the practical Canadian fixes, from a simple hygrometer up to a full insulation upgrade, that dry the space out.

Why This Matters More Than a Few Droppings

It is easy to shrug off a mouse in the garage as a nuisance rather than a hazard, but there are real reasons to take it seriously. Health Canada notes that mice and rats are carriers of disease and can damage property, and that the deer mouse, common near fields and woodlots across rural and suburban Ontario, is the most frequent carrier of hantavirus. That is why the cleanup advice below matters so much.

Property damage is the other underrated risk. Rodents have continuously growing front teeth and gnaw constantly to keep them in check, and one of the things they gnaw is wiring. In a garage, that can mean the wiring behind your opener, your lighting circuits, or a stored appliance, and chewed insulation on a live wire is a genuine fire and failure risk, not just an inconvenience. A mouse problem caught early and sealed out is far cheaper than a chewed harness or a damaged opener later.

If Pests Are Already Inside: Safe, Accurate Control

Sealing the door keeps new pests out, but if you already have visitors, you will need to deal with them too. Health Canada's guidance is worth following closely here, because some of the common instincts are exactly wrong.

For mice and rats

Snap traps and electronic traps are easy to use and, set correctly, are very effective. Place them at right angles to the wall with the baited end toward the wall, and use small amounts of a sticky, strong-smelling bait like peanut butter. Health Canada cautions that baits and poisons should never be the only method, that any poison bait must be used in a tamper-proof bait station where children or pets could reach it, and that prevention and sanitation still have to be part of the plan. For the full method, see Health Canada's rats and mice page.

The cleanup deserves real care. Health Canada is explicit that you should never sweep or vacuum dry droppings, because the dust that gets stirred up can carry disease. Instead, wear rubber gloves and a dust mask, dampen droppings and debris with a bleach-and-water solution before wiping them up, double-bag the waste, and wash up thoroughly afterward.

For wasps

If a wasp nest has appeared in a garage corner or under the eave, Health Canada's advice on wasps is to act with caution. A nest that is not an immediate hazard is best left until late autumn, when it is naturally abandoned and can be removed safely. If a nest must come down while it is active, it should be dealt with after dark when wasps are least active, with protective clothing, and professional help is recommended for anything beyond a small, easily reached nest. For the wider list of common household pests and their specific control tips, Health Canada keeps a useful index of pest control tips.

Build It Into Your Routine

Pest-proofing is not a one-and-done project, because seals wear and habits slip. The good news is that the same monthly garage door check that keeps your door running safely is the perfect moment to glance at the seals and the corners. The garage door industry association DASMA recommends a regular look at the door and its hardware as part of routine garage door maintenance, and adding a quick flashlight test for gaps takes only a minute. Our monthly garage door safety test is a natural home for it.

Twice a year, ideally in spring and fall, take a closer look: run the flashlight test, press on the bottom seal to check it is still flexible rather than cracked, confirm the side and top seals still touch the door, and clear any new clutter or food that has crept back in. Caught at this stage, a tired seal is a sixty-dollar afternoon. Ignored, it is the open door that lets the next problem in.

Frequently Asked Questions

How small a gap can a mouse really get through?

Smaller than most people expect. Health Canada states that a mouse can squeeze through a crack as small as a dime and a rat through a hole the size of a quarter, and it specifically warns that even the small gaps left by a worn threshold under a door are enough to let mice in. If you can see daylight under or beside your closed garage door, that gap is large enough to matter.

Will a new bottom seal alone keep mice out?

Often, but not always. A fresh, flexible bottom seal is the single most important fix and solves most cases. But if your concrete floor is uneven, the seal will bridge over the low spots and leave a channel underneath. In that situation you also need a threshold seal that bonds to the floor and rises to meet the door. The two together close the floor line completely.

What is the most common pest entry point on a garage door?

The bottom of the door, followed closely by the two bottom corners where the side seals meet the bottom seal. Both are easy to check with a nighttime flashlight test and both are fixable with replacement weatherstripping. The sides and top of the door are next, especially on older doors where the perimeter jamb seals have shrunk or gone missing.

Is it safe to use mouse poison in my garage?

Health Canada advises that baits and poisons should never be the only control method and that any poison bait must be placed in a tamper-proof bait station wherever children or pets could reach it. Always look for a Pest Control Products (PCP) number on the label so you know the product is approved, and follow the label directions exactly. For most homeowners, sealing the gaps plus well-placed snap traps is safer and more effective than poison.

Why shouldn't I just sweep up the droppings?

Because sweeping or vacuuming dry droppings stirs up dust that can carry disease, including hantavirus from deer mice. Health Canada recommends wearing gloves and a dust mask, dampening the droppings with a bleach-and-water solution first, wiping them up, double-bagging the waste, and washing thoroughly afterward. Never dry-sweep or dry-vacuum a rodent mess.

Should I keep my garage door closed to keep pests out?

Yes. Leaving the door open, even partway, removes every seal you have installed and gives pests an open invitation. Keeping the door closed when you are not actively using it is the simplest pest-control habit there is, and it helps with security and energy use too. If you tend to forget, an auto-close timer or a smart opener that alerts you when the door is left open can do the remembering for you.

Do ultrasonic pest repellers work?

The evidence is mixed. Health Canada notes that ultrasonic devices give off sound or vibrations that rodents dislike, but that rodents may adapt to them and return, so they should only be used alongside other methods rather than on their own. Sealing the gaps and removing food and water will always do more than a plug-in device.

The Bottom Line

The garage door is the largest opening in your home, which makes it both the easiest way for pests to get in and one of the most controllable to lock down. Start at the bottom, because the bottom seal is the most common entry point and the cheapest to fix. Close the floor gap with a threshold seal if your slab is uneven, seal the sides and top with fresh jamb weatherstripping, and pay special attention to the two bottom corners where so many mice slip through.

Then do the behavioural half: store food in metal or glass, cut the clutter, dry up the moisture, and keep the door closed. None of it is expensive and most of it is a weekend afternoon, but together it turns the biggest door on your house from an open invitation into a closed one. If you would rather have a professional inspect and reseal the door properly, that is exactly the kind of work we do every week.

We have been keeping London-area garage doors sealed, balanced and weather-tight since 2009, and our record is public on our BBB profile. We are always glad to take a look and tell you honestly whether a reseal or a repair is all you need.