The cheapest way to deal with rats and mice is to never let them in. Traps and poison fight a problem that already exists. Sealing the place up keeps the problem from starting, and it is the one pest control job that genuinely pays for itself.
Mice can fit through a gap the size of a dime, so the bar is higher than most people think. Here is how I go through a house and close it up.
Seal the entry points
Rats and mice get in through the same predictable spots, so work through this list top to bottom.
- Gaps around utility pipes, wires, and cables where they enter the house. This is the most common entry point.
- Cracks in the foundation, especially where it meets the sill plate.
- Gaps under exterior doors, missing or worn door sweeps.
- Crawlspace vents with damaged or missing covers.
- Attic, gable, soffit, and ridge vents without screens.
- The gap under a garage door, especially if the weather seal is damaged.
- The space around a dryer vent pipe where it exits the wall.
- Roof junctions, where the roofline meets siding, chimneys, and skylights.
- Loose or damaged siding, especially at corners and trim.
- Worn weatherstripping around windows, especially basement windows.
Use the right material for each gap
- Copper mesh: for small gaps up to about half an inch. It does not rust and lasts for years. Stuff it around pipes and wires.
- Expanding foam: for irregular gaps. Use the pest-block kind, and put copper mesh in first so they do not chew through the foam.
- 1/4 inch hardware cloth: for vents and larger openings. Galvanized steel, attached with screws and washers.
- Hydraulic cement: for foundation cracks and masonry. It dries hard and rodents cannot chew it.
- Door sweeps and weatherstripping: on every exterior door and window.
A tip on steel wool: a lot of advice says to use it, but plain steel wool rusts and crumbles in months and leaves the gap open again. Copper mesh costs a little more and actually lasts.
Cut off the food and water
Sealing is half the job. The other half is making your place not worth the trip:
- Store pet food and birdseed in sealed metal or heavy plastic bins.
- Do not leave pet food out overnight.
- Pick up fallen fruit and nuts from the yard.
- Keep garbage in cans with tight lids.
- Fix leaky pipes and faucets, rodents need water too.
- Keep counters and floors free of crumbs.
Frequently Asked Questions
With the right materials, years. Copper mesh and hardware cloth are basically permanent. Foam and caulk may need a touch-up now and then.
Yes, most of it. Foundation cracks, door sweeps, and vent covers are all DIY-friendly. Sealing a complicated roofline is where a professional earns their pay.
Doing it yourself is cheap, a roll of copper mesh, some foam, and a few door sweeps cover most houses. Hiring it out costs more and depends on the size of the house and how many gaps need work.
Yes. The same sealing that stops rats and mice also stops squirrels, raccoons, snakes, and insects. It is one of the better investments you can make in a house.
About the width of a dime, around a quarter inch. If a pencil can fit under a door, so can a mouse.
