Mouse-Proofing Your Garage Before Winter: A Guide for Lancaster Homes

    By Desert Grizzly Pest Control · Reviewed by George Barahona, owner · Last updated: October 19, 2026

    On a lot of Lancaster streets, the garage is the busiest door in the house. It's where the car, the pet food, the extra pantry stock and years of stored boxes all live. It's also the room most likely to have a gap at the bottom of the door. When the high desert nights start getting cold, that combination makes the garage the easiest place for a mouse to move in.

    This guide is just about the garage: how to tell if mice are using it, how to seal it up before winter, and how our Preventative Rodent Protection helps keep them outside. It's written with east Lancaster (93535) in mind, where many homes sit near open desert lots, but it works for any garage in the Antelope Valley.

    Why the Garage Is the First Stop for Mice

    According to the University of California's Integrated Pest Management program (UC IPM: House Mouse), where outdoor house mice live, they often move into homes in autumn when nighttime temperatures drop.

    Garages make it easy:

    • They have the biggest openings in the house. A garage door that doesn't seal tight at the corners is a ready-made entrance.
    • They hold food. Bags of dog food, birdseed and bulk pantry items are often stored there.
    • They're full of shelter. Boxes, piles of rags, and cluttered corners make good nesting spots.
    • They're quiet at night, which is when mice are most active.

    UC IPM notes that mice can get through openings as small as 1/4 inch. That's a very small gap, so a garage door that looks "mostly closed" can still let them in.

    Signs Mice Are Using Your Garage

    UC IPM lists these signs of house mouse activity:

    • Droppings along walls, on shelves, or near stored food
    • Fresh gnaw marks on boxes, bags, plastic bins or wood
    • Nests made of finely shredded paper or other fibrous material, often behind boxes or in drawers
    • A musky odor, which is common in larger or long-term infestations
    • Tracks in dust along the floor or shelves

    In a garage, also look for chewed-open pet food or birdseed bags, and shredded cardboard in the corners.

    Found droppings? Don't sweep or vacuum them dry. Follow the safe cleanup steps in our Palmdale mice and rats guide, which links to the CDC's instructions.

    Start With the Garage Door

    The main door is the most common weak point, so check it first:

    1. Close the door and look from inside with the lights off on a bright day. Daylight showing at the bottom corners or along the sides means there's a gap.
    2. Check the bottom seal for cracks, flattened sections, and chewed corners.
    3. Look at the side tracks and the door frame where the door meets the wall.
    4. Check the side or back door too. It needs a tight door sweep and threshold.

    UC IPM says doors, windows and screens should fit tightly, and that it may be necessary to cover the edges of doors with metal to prevent gnawing. If you see chew marks at the corners of the bottom seal, that's a sign the seal alone isn't stopping them.

    Seal the Rest of the Garage: What Works and What Doesn't

    UC IPM calls exclusion the most successful and permanent form of house mouse control. Walk the inside and outside of the garage and look for:

    • Cracks in the foundation or slab edge
    • Gaps around water pipes, gas lines, and electrical or cable lines coming through the wall
    • Gaps around the water heater vent and other wall vents
    • Openings where the garage wall meets the house

    What to use, per UC IPM:

    • Works: wire screen, coarse steel wool, metal or concrete. UC IPM notes steel wool makes a good temporary plug but may rust over time.
    • Doesn't work: plastic screening, rubber, vinyl, expanding foam, wood and other materials mice can chew through.

    Make the Garage Less Inviting

    Sealing is the main fix, but a tidy garage gives mice fewer reasons to try. These steps follow UC IPM's advice:

    1. Store pet food, birdseed and pantry items in sealed containers. UC IPM notes mice can chew through storage containers, so sturdy, tight-lidded ones are best.
    2. Feed pets only what they'll eat at one feeding, and don't leave bowls out overnight in the garage.
    3. Keep garbage cans sealed.
    4. Cut down on clutter and cardboard. Fewer hiding spots means mice can't settle in large numbers. Lifting stored items off the floor also makes it easier to spot droppings early.
    5. Trim plants and vines growing next to or up the garage wall. UC IPM says house mice are excellent climbers and can run up rough vertical surfaces.

    Cleaning out the garage this fall? Wear gloves. Garages are also a favorite spot for black widows. See our guide to black widows in block walls and garages.

    Protect the Car and the Door Into the House

    Two things make garage mice more than a nuisance:

    • Your car. UC IPM notes that house mice can damage structures and vehicles by gnawing on electrical wires. If you park in the garage, that's one more reason to keep them out.
    • The door into the house. Once mice are in the garage, the next step is often the house itself. Make sure the door between the garage and the house has a tight sweep and weatherstripping, and check where pipes or wires pass from the garage into the walls of the house.

    If Mice Are Already in the Garage

    • Trapping is UC IPM's preferred method in homes and garages when only a few mice are present. Set snap traps close to walls, behind objects and in dark corners where you've seen droppings. UC IPM notes mice seldom travel more than about 30 feet from their nest and food, so space traps no more than about 10 feet apart in active areas.
    • Keep traps away from kids and pets. Set them where they can't reach.
    • Skip the plug-in repellers. UC IPM says high-frequency electronic devices aren't effective.
    • Bait stations: UC IPM notes that rodenticides sold for home use in California come only in ready-to-use bait stations, that all rodenticides are toxic, and that baits should be kept out of reach of children, pets and wildlife.

    If you're catching mice often, or you're not sure where they're getting in, call George at 661-990-PEST (7378) and tell him what you're seeing.

    Preventative Rodent Stations: $160 Setup + $20/Month

    For a lot of Lancaster homes, especially near open land, the goal is to stop mice before they reach the garage at all. That's what our Preventative Rodent Protection is for:

    • $160 one-time setup to place rodent bait stations around the outside of your home
    • $20 a month for ongoing service

    Want everyday pests covered too? Our $60 general pest control is a flat $60 whether you choose monthly, bi-monthly, quarterly or one-time, with no startup fees and no bait-and-switch. See the Lancaster pest control page for the areas we serve.

    Garage Mouse FAQs

    Why are mice showing up in my garage now? UC IPM notes house mice often move into homes in autumn as nights get colder. A garage with a gap under the door is usually the easiest way in (source).

    Can I fill the gaps with expanding foam? UC IPM says foam, rubber, vinyl, plastic and wood are ineffective because mice can chew through them. Use wire screen, coarse steel wool, metal or concrete instead.

    Do ultrasonic repellers keep mice out of the garage? UC IPM says high-frequency electronic devices aren't effective against house mice.

    How much are rodent bait stations in Lancaster? Desert Grizzly's Preventative Rodent Protection is $160 for setup plus $20 a month.

    Do you serve east Lancaster? Yes. We cover 93535, 93534 and 93536 in Lancaster, plus Palmdale (93550, 93551, 93552).

    Call George: 661-990-PEST (7378)

    Finding droppings or chewed bags in the garage? Call 661-990-PEST (7378). George answers his own phone.

    • Rodent stations: $160 setup plus $20/month
    • General pest control: $60 flat (monthly, bi-monthly, quarterly or one-time), no startup fees
    • German roach treatment: $200 for 3 visits
    • Service ZIPs: 93535, 93534, 93536 (Lancaster) · 93550, 93551, 93552 (Palmdale)

    Desert Grizzly Pest Control · 2040 W Ave J13 #3, Lancaster, CA 93536 · Locally owned and operated California Structural Pest Control Board Company Registration PR 10146

    Sources