Pull a dime out of your pocket and look at it. That’s roughly the size of the doorway a mouse needs to get into your house.
According to Penn State Extension, a mouse can slip through an opening about as wide as a dime or a pencil. Rats need something closer to a quarter. Either way, you’re not looking for a big hole. You’re looking for a lot of small ones.
And right now, they’re looking for you. University of California pest experts say mice frequently move into homes in autumn, once nights turn cold.
Here’s the problem: The store aisle is stocked with the wrong answers. Poison pellets, glue boards, bug foggers and plug-in gadgets that promise to scare mice away with sound. Much of it either doesn’t work or creates a new problem.
The fix that university extension experts actually recommend is duller: Seal the gaps, set the right traps, and clean up without making yourself sick. Here are seven ways to do it.
1. Seal the dime-size gaps — with the right stuff
Get a flashlight and walk the outside of your house, then the inside.
The Centers for Disease Control and Prevention says to check where pipes run beneath sinks and behind the washing machine, every place a utility line comes through a wall, dryer and floor vents, and vents in the attic and crawl space.
What you plug them with matters. Penn State recommends rodent-proof materials: copper mesh, silicone sealant and hardware cloth. The CDC suggests steel wool for small holes, held in place with caulk or spray foam, and sturdier stuff like metal sheeting, cement or hardware cloth for bigger ones.
Stop relying on foam by itself. University of California experts list expanding foam, along with plastic screening, rubber, vinyl and wood, as gnawable materials that mice can chew right through.
Steel wool has a weakness, too. The same UC guide says it makes a decent temporary plug but can rust over time. That’s why copper mesh is a smart upgrade for gaps that’ll be exposed to moisture.
2. Fix the doors, including the garage
One of the easiest gaps to overlook is the one under the door. Both Penn State and NC State recommend installing door sweeps on exterior doors. It’s an inexpensive hardware-store fix most people can handle with a screwdriver.
The CDC also flags windows and doors that lack weather stripping as trouble spots, and it says to seal garages and outbuildings, too. If daylight shows under your garage door, a mouse sees an open invitation. Replace a worn-out bottom seal before the first hard freeze.
3. Lock up the buffet
Mice don’t move in for the view. They come for food and shelter, and most houses offer both.
The CDC says to keep food in tightly lidded containers made of glass, metal or thick plastic. Penn State says to keep it off the floor. That includes the big bag of dog food in the garage, which is an all-you-can-eat sign to anything with whiskers.
Cardboard boxes and paper bags won’t stop them. UC experts note mice can chew on containers that are supposed to protect food, so go hard-sided.
The CDC also says to clear away pet food once your animals finish eating rather than leaving bowls out overnight, and to hang bird feeders well away from the house.
4. Clear the perimeter
Mice love cover. A woodpile stacked against the siding is basically a rodent hotel with a shuttle to your kitchen.
The CDC recommends stacking firewood at least 100 feet from the house and raising it a foot or more off the ground. It also says to keep the grass and shrubs near your home — anything within 100 feet — trimmed.
UC adds that trees and shrubs shouldn’t touch the foundation. If you’re already out there doing fall chores that prevent a $30,000 burst-pipe claim, add this to the list.
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5. Use snap traps, not glue boards
If mice are already inside, sealing alone won’t evict them. You need traps — and the old-fashioned kind wins.
The CDC recommends traditional snap traps and says to skip glue and live traps. Its reason is practical: A frightened rodent may urinate, which raises your odds of getting sick. Penn State also advises against glue boards.
Placement is everything. Mice prefer to run along walls, so put the trap on the floor with the baited end against the wall, forming a T. A dab of peanut butter works well as bait, according to both the CDC and Penn State.
Use more traps than you think you need. UC’s house mouse guide suggests setting them roughly 10 feet apart, or closer, where you see activity. That matters, because a single female can produce five to 10 litters a year.
6. Keep poison and bug bombs out of the house
Here’s the one that makes me crazy. The most heavily marketed products are often the worst choices for the inside of your home.
Penn State’s advice is blunt: Avoid rodenticides inside homes. The reason? Poisoned mice often die inside your walls, where they smell and draw insects. Good luck finding the one behind the drywall.
Then there’s the risk to everyone else who lives with you. The Environmental Protection Agency warns that misused mouse and rat poisons can harm you, your kids and your pets.
The EPA says to put baits only in spots kids and pets can’t get to. The CDC says to reserve poison for infestations that persist.
As for bug foggers and sprays, Penn State says they’re made to kill bugs and do nothing to rodents. And those plug-in ultrasonic gadgets? UC experts say ultrasonic sound is of very little use against rodents. Save your money.
7. Clean up droppings without making yourself sick
This is the step people get wrong, and it’s the one that can actually hurt you.
Rodents can carry hantavirus, which the CDC says can make people seriously ill or even kill them. The virus gets into the air when fresh droppings, urine or nesting material are disturbed, and you get infected by breathing it in. So don’t sweep or vacuum.
Instead, follow the CDC’s cleanup steps. First, prop open doors and windows, leave the area and let the place air out for half an hour.
Put on rubber or plastic gloves. Spray the mess with a bleach solution — 1.5 cups of bleach per gallon of water — and give it 5 minutes to soak.
Then wipe it up with paper towels, toss them in a covered trash can, and once the gloves are off, wash up with warm, soapy water.
The bottom line
The pest aisle wants you to buy a solution in a box. The experts at Penn State, NC State, the University of California and the CDC all point the other way: Shut the doors mice use, take away what they’re after, and catch the ones already inside.
Most of that costs a few rolls of mesh, a tube of sealant, a door sweep and a pack of snap traps. Do it now, before the weather turns, and you may never need to deal with what the next big storm can send indoors.
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