How Mice Get Into a House: Entry Points Technicians Find First
Homeowners in Brooklyn and Queens often ask the same thing: where do mice come from? In a freestanding house they use gaps that look too small to matter. This post lists the entry points technicians check first and a simple test you can do yourself.
Start with the pipes and utility lines
Holes where pipes, cables and conduit enter the house are the most common entry points. Plumbing for kitchens and bathrooms, gas lines, cable and phone lines, and the pipes for heating and air conditioning all pass through walls, and the gap around them is often left open or filled with something mice can chew.
Look at work done by other trades
A frequent cause is a recent repair. When sprinkler installers replace a pipe, or a utility company runs a new line, the hole they leave can stay open for years. If mice appeared a few weeks after any work in the walls or foundation, check that spot first.
Doors, garage and basement
A garage door with worn seals, a basement door that does not close tight and a door sweep with a gap are easy routes. A mouse needs only a gap about the width of a pencil. Check the bottom edge of every exterior door.
Vents, central air and rooflines
Unscreened vents, openings around central air lines and gaps at the roofline give mice and rats a way in. Screening vents with metal mesh and sealing line penetrations solves most of this.
The daylight test
Go into the basement or the lowest level and look at the places where the building meets the foundation. If you can see daylight through a gap, a mouse can get through it. Walk the whole perimeter and mark each spot. This simple check often finds more entry points than expected.
Why sealing comes before bait
Technicians seal first because bait without sealing only deals with the mice already inside. Once the entry points and the paths mice use inside walls, near kitchen plumbing, bathroom plumbing, heat sources and closets are closed, a few bait stations or traps finish the job. A one year written warranty is common for some jobs, but ask what it covers.
What a house job typically costs
In New York City, a three level single family house with mice commonly falls in the $195 to $550 range for mouse control in 2026, with extra sealing quoted by the number of openings. Larger houses and heavy activity cost more. Read our mouse exterminator cost guide for the full breakdown.
Frequently Asked Questions
Where do mice usually get into a house?
Around pipes and utility lines, at doors and garage seals, through vents and at the foundation line.
How small a hole can a mouse use?
About the width of a pencil, roughly a quarter inch.
What is the daylight test?
Inspect the foundation line from inside. Any gap that lets light through can let a mouse through.
Should I use bait or seal first?
Seal first. Bait alone does not stop new mice from coming in.
