Mice can squeeze through any gap that’s at least ¼ of an inch wide–about the size of a dime! They find these gaps by following the smell of food or feeling of air pressure differentials created by drafts. Mice are very adept climbers, so they can reach gaps anywhere around your home.

After using tiny gaps to sneak inside, mice can reproduce all year as long as they have food. Mice had to sneak in originally, but many of the mice you find in your home were likely born there. The best way to keep mice out of your home for good is to seal off their access points. These are the four most common ways mice get inside homes and how you can mouseproof them.

Frames

Believe it or not, door and window frames are probably the access points mice use most. Wooden frames naturally warp and bend over time, creating small gaps between the window or door and the frame. Likewise, the weatherproofing wears down or unpeals. Eventually, tiny gaps appear between the door or window and frame or the walls and the frame. These gaps may not be large enough to see, but they’re large enough for mice to use.

Conduct a quick maintenance inspection on each of your door and window frames every spring and fall. Replace any weatherproofing that looks worn down or damaged. Check to make sure the doors and windows sit in the frame properly and don’t feel too tense or loose. Patch up any cracks or gaps you find around the wood itself using caulk. If you can feel a draft, it means your frame isn’t as secure as it should be. Find the gap sucking hot air out and patch it up.

Utility Lines

Utility lines are the pipes, wires, and vents bringing gas, electricity, heat, and plumbing into your home. All homes need to have small gaps in their walls to allow these utility lines inside. The problem is, mice can find these gaps by following the utility lines. They’ll sense heat given off by ventilation or hot water and follow that heat through the wall. Gaps between walls and utility lines may expand over time, making the gap an even more attractive access point.

Starting outside, walk the perimeter of your home looking for each area where a utility line enters the building. Look near your HVAC, your power meter, your sump pump, your light fixtures, and your outdoor faucets. If you see a visible gap between these pipes or wires and the wall, patch that gap with caulk. When you’re done outside, go inside and do the same thing. Replace these caulk barriers around once a season to make sure they don’t wear away.

A small gap between a basement's wall and its concrete floor. Mice often sneak through the space gaps like these create.

Subterranean Gaps

Over time, cracks and gaps may open up around the foundation, siding, or the baseboarding of your home. These could occur because of weather damage, wood rot, or natural wear-and-tear. However they happen, small gaps and cracks around your home’s foundation start to create drafts. These kinds of drafts are particularly common in unfinished basements. Mice are very sensitive to temperature and pressure differentials. When they sense the hot air shooting out of gaps in a home, they’ll follow it inside.

Start in your basement or lowest level this time. Look for cracks and gaps in the floor and ceiling. Pay particular attention to corners, windows, baseboard, and frames. Seal any gaps you can find with silicone caulk or steel wool. Remember: if a crack or gap is big enough to see, it’s probably big enough for mice to use. Just like before, when you’re done inside you should look for cracks and gaps outside, too.

Roofing

Mice are surprisingly adept climbers. Most mice are capable of climbing most homes without much difficulty by finding downspouts, wires, or other holds. Mice can also access rooftops by climbing up nearby trees or bushes and crawling along overhanging branches. Unfortunately, the fact that mice can climb so well means no access point is safe. Mice don’t just sneak inside from the ground; they could be sneaking in from the roof, too!

Even worse, roofs tend to have all kinds of neglected access points. Mice can exploit rotting shingles, ventilation outlets that aren’t covered, chimneys, cracked gutters, and more. If you have roofing damage, mice will likely use that damage as a means of entering your home. You should have your roof inspected at least once every few years. Check for cracked shingles, rot, and other possible damage. You should also always block your vents and chimneys with mesh.

 

The best way to prevent mouse infestations is to continuously monitor and block off access points. Check each of the most vulnerable areas every spring and fall to make sure you’re still covered. If you stay on top of your access point maintenance, you’ll keep mice from infesting your home for good.

If you already have a mouse infestation inside your home, even blocking off access points won’t help right away. Instead, you’ll have to call the pros at Griffin Pest Solutions. We can drive out mice and make sure they can’t get in again. Mouse season is starting right now, so if you think you have a problem, get in touch right away! We’ll help make sure you have a rodent-free fall. 

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