No Mice Here Mouse-proof my house
Regional guide · California

The Central Valley: the mouse-proof standard.

The same 10 spots, in the order that fits how homes here are built. Every home can be made mouse-proof, and mice come in for shelter, so sealing the gaps is what keeps them out.

How homes here are built

In the middle of the state, crawlspaces start to take over from basements. Crawlspace vents are a common way in for animals, so start low and work your way up.

The mouse-proof standard. Every home can be made mouse-proof. Seal for the smallest invader, the mouse, and you’ve closed the gaps the bigger ones use too. What the standard means →

Where to look first

  • Crawlspace vents

    Cover each vent with 1/4-inch hardware cloth (stainless or heavy galvanized). Never block a vent.

    The foundation line
  • The crawlspace access door

    Check that the access door fits tight, with no daylight around it.

    Doors
  • Lines into the crawlspace

    Pipes, cables and AC lines often enter through the crawlspace wall. Check each one with the finger-width rule.

    Utility lines
  • AC line sets

    Look where the AC lines go through the wall to the unit outside.

    AC line sets
  • Soffit vents

    Soffit vents under the eaves are another way in. Screen them with hardware cloth too, and keep them open.

    Rooflines and soffits

Rats, pigeons and bats use gaps like these too. Seal to the mouse-proof standard and those gaps are closed to them as well: one standard, not a separate fix for each animal.

Check for bats before you seal

Before you seal any gap up high, shine a strong flashlight up into the shadow: rooflines, roof returns, attic and soffit vents. Look for droppings, dark rub stains, a clean hole through the cobwebs, or bats tucked in the gap. If you see any, don’t seal it yourself, because bats need a proper exclusion so none get trapped inside.

Never seal anything in. If something could be living behind the gap, don’t seal it yet. On a two-story house, when in doubt, assume bats. Don’t touch a bat, alive or dead (CDPH). If you think you’ve had contact with one, talk to your health department (CDC).

More on bats in California →

The common mistake: stuffing a gap with steel wool or foam. Mice chew through foam, and steel wool rusts and pulls apart, so the gap opens again. Neither one is a lasting seal.

Mice and hantavirus here

The hantavirus that makes people sick in California, Sin Nombre virus, is spread by deer mice, which are found throughout California (CDPH). CDPH says the best way to prevent it is to keep wild rodents, especially mice, out of your home, workplace, cabin, shed, car or camper (CDPH).

Deer mice live in forests, grasslands and farmland, and they often move into homes and cabins that sit empty (UC IPM). UC’s pest experts call exclusion the most effective and permanent way to keep them out, and note that foam, plastic and rubber don’t work as plugs (UC IPM).

Fever or trouble breathing after being around rodents? Talk to a healthcare provider and mention deer mice (CDPH).

Catch the ones inside once

Once the outside is sealed, catch any mice still inside with enclosed snap traps set along the walls, out of reach of kids and pets. CDPH recommends snap traps, not glue traps or live traps (CDPH). Never poison.

Clean up droppings safely

  1. Open doors and windows for 30 minutes first, and stay out while it airs.
  2. Put on rubber or plastic gloves.
  3. Don’t sweep or vacuum droppings. It puts dust into the air.
  4. Spray droppings and urine with a disinfectant, or 1 part bleach to 9 parts water, until very wet. Let it soak 5 minutes.
  5. Wipe up with paper towels and throw them out in a covered trash can.
  6. Mop or wipe the area with disinfectant, then wash your gloved hands, take the gloves off, and wash your hands again.

Source: CDC, How to Clean Up After Rodents. Asthma or allergies at home? Mouse allergen settles in household dust, and NIEHS researchers linked higher levels at home to more asthma symptoms in people with allergies (Salo et al., 2009). Sealing the gaps and cleaning up this way both help.

CDPH gives California homes the same clean-up steps (CDPH). Your local mosquito and vector control district can help too: find yours on the MVCAC list of member agencies.

Pro matching is in Southwest Florida for now. The free basic check and the guides work anywhere. Not sure what you’re looking at? Send a photo.

Sources

  1. California Department of Public Health (CDPH), Hantavirus Infection
  2. University of California Statewide IPM Program, Deer Mouse: Pest Notes
  3. California Department of Public Health (CDPH), Rabies
  4. Centers for Disease Control and Prevention (CDC), Preventing Rabies from Bats
  5. Centers for Disease Control and Prevention (CDC), How to Clean Up After Rodents
  6. Mosquito and Vector Control Association of California, Member agencies

Health facts on this page were checked against each source on October 30, 2026.

Find the gaps. Seal them for good. Catch the ones inside once. No poison, ever.