They Don't Knock — How Mice Are Getting Into Your House Right Now

Every October, like clockwork, my phone starts ringing with the same call: "I'm hearing something in the walls." Sometimes it's scratching at night. Sometimes it's a scurrying sound over the ceiling right when everyone's trying to fall asleep. And almost every time, the homeowner says the same thing — "but I don't know how anything could have gotten in."

I get it. You look at your house and you see a solid building. Doors that close. Windows that lock. But a mouse doesn't see your house the way you do. A mouse sees a dozen open doors you've never noticed — and when the first cold week of fall hits Staten Island, every mouse in the neighborhood goes looking for them.

So today I want to walk you around your own house the way I walk around it on an inspection. Because once you know where to look, you'll never un-see this stuff.

The dime test

Here's the number that surprises everyone: a full-grown mouse can fit through a gap about the size of a dime. A quarter inch. Their skeleton is built to compress — if their skull fits, the rest follows. Young mice need even less.

So when I do an inspection, I'm not looking for "holes." I'm looking for anything a pencil could slide into. That changes the whole picture of a house.

Where I actually find them getting in

After thousands of inspections around Staten Island, Brooklyn, and the NJ side, the same spots come up over and over. The biggest one? Where pipes and wires enter the house. Your gas line, your water line, your AC line, your cable — every one of those goes through a hole in your foundation or siding, and the hole is almost always bigger than the pipe. Builders rarely seal them tight, and even when they do, the sealant cracks over the years.

Second on the list is the garage. Look at the rubber strip at the bottom of your garage door. If it's worn, cracked, or chewed at the corners — and most are — that's an entry the width of your entire driveway. Once a mouse is in the garage, the door to the house is usually a much easier puzzle.

Then there's the stuff nobody ever thinks about: the little weep holes in brick walls (they're supposed to be there — they drain moisture — but they're perfectly mouse-sized), dryer vents with flaps that don't close right, torn screens on crawl space vents, and gaps up at the roofline where the wood has warped over the years.

And one more, because I see it on almost every job: bushes and ivy growing right up against the house. That greenery is a covered highway. Mice run along your foundation completely hidden, taking their time, checking every inch for a way in. Trim everything back a foot from the wall and you take away their cover.

The mistake people make once they're inside

Here's the one thing I really need you to take from this post. If mice are already in the house, don't seal the holes first.

I know it feels backwards. But if you seal every gap while mice are still living in your walls, you've just locked them inside your house. They'll either chew a new way out — or they won't, and a few weeks later you'll be calling me about a smell instead of a sound. Trust me, you want the sound problem.

The right order is always: confirm what you're dealing with, eliminate the population, then seal everything up so the next wave can't move in. That last step — the sealing, what we call exclusion — is honestly the most important part, and it's the part most exterminators skip because it's actual work.

What you can do this weekend

Walk your house slowly, at ground level, and look at every spot where something enters the building. Pipes, wires, vents, the corners of the garage door. Bring a flashlight even in daylight — shadows hide gaps. If you find small openings, steel wool packed in tight and sealed over with caulk does the job for most of them. Mice hate chewing steel wool. Foam alone doesn't stop them — they go through it like bread.

And if you find droppings, take a picture before you clean up. Fresh ones are dark and soft-looking; old ones are gray and dusty. That tells me how active the problem is before I even get there, and it means I show up with the right plan on the first visit.