Deer Mice in Garages and Sheds: Cleanup and Keeping Them Out
Open the doors and leave for at least 30 minutes, soak every dropping and nest with bleach solution before touching it, then fix the gaps that let mice in: the bottom of the door, the floor edges and any vents. That order keeps you safe and keeps the problem from coming back.
Garages and sheds are where deer mice and people meet most often around Albuquerque. They're quiet, full of stored stuff and usually leakier than the house. The New Mexico Department of Health singles out cabins, sheds, garages and stored vehicles in its hantavirus advice for that reason.
Why outbuildings draw deer mice
NMSU Extension calls the deer mouse a field rodent that comes indoors mostly in cold weather. The nearest building to the brush is usually a shed, a detached garage, a casita or a pump house. Inside, they find nesting material in boxes, old cushions and rags, and food in birdseed, grass seed, pet food and feed.
Homes on the edge of open land get the most of this. That includes the mesa around Mesa del Sol and Westgate and the rural lots in Edgewood and Moriarty.
Signs they've moved in
Look for these on your next trip to the shed:
- Droppings on shelves, in drawers and along the floor edge
- Shredded paper, insulation or fabric in boxes
- Chewed seed or feed bags
- A musty smell when you open the door
- Nests in seldom-used gear: coolers, boots, mower bags
Cleaning up safely
Follow the CDC steps for outbuildings. Open all doors and windows and leave for 30 minutes. Put on gloves. Spray droppings and nests with fresh bleach solution (1.5 cups of bleach per gallon of water) until very wet, wait 5 minutes and wipe up with paper towels. Spray dirt floors with disinfectant. Move stored boxes outside into the sun, throw out contaminated cardboard and stand upwind of any dust.
Never sweep or use a shop vac. For a small shed or a heavy mess, NMSU recommends a HEPA or N-100 respirator. The full method is in hantavirus-safe cleanup.
Sealing a garage
Most garages leak at the door. Close the door on a sunny day and look for light at the bottom and corners. A new bottom seal and corner pieces close most of it. Then check the service door sweep, the gaps around the water heater flue and any wall penetrations. NMSU says a quarter-inch hole is enough for a mouse, so be thorough. Rodents in cars and garages covers the rest.
Sealing a shed
Sheds are harder. Plywood floors on blocks have gaps at the edges, siding may not reach the ground and doors rarely latch tight. Closing them takes metal:
- Quarter-inch hardware cloth along the base of the walls and floor edge
- A metal sweep or strip along the bottom of the door
- Screens on vents and any gable openings
- Feed and seed in metal cans with tight lids
- Stored fabric and cushions in sealed plastic bins
Trapping
Use snap traps. The state rodent guide says glue boards and multi-catch live traps shouldn't be used for deer mice, and that mice caught alive shouldn't be released outside. Set traps along walls where droppings are fresh. Disinfect and double-bag every catch. If the catch keeps coming, there's a gap you missed. Cabin and shed rodent control is the service to call.
Storing things so mice can't use them
Mice nest in what's easy to shred: cardboard, paper, fabric, insulation and the stuffing from old furniture. Move those into sealed plastic bins with tight lids. Put birdseed, grass seed, dog food and chicken feed in metal cans. Keep things off the floor on metal shelves, with a little space between the shelf and the wall so you can see behind it. The less there is to hide in, the faster you'll notice a mouse.
Checking it stays fixed
Leave two or three snap traps along the walls after you've sealed. Check them once a week through the fall. If they stay empty and no new droppings show up on the shelves you cleaned, the sealing worked. A catch means there's still a gap, often at a door corner or where a pipe enters the wall. Look again on a sunny day with the door closed and the lights off, and watch for light coming through.
When to call a provider
Call when the shed is too small to air out well, when nests are in insulation or stored furniture, when you keep catching mice after sealing or when someone in the house has lung or immune problems. A provider can trap, clean with proper gear and seal the outbuilding in one job. See cabin and shed rodent control and the cost guide for typical prices.
Also asked
Can I just leave the shed alone?
Mice will keep breeding and the mess will grow. Clean and seal it before you need to get in there in a hurry.
Is it safe to store dog food in the garage?
In a metal can with a tight lid, yes. Open bags draw mice from across the yard.
Should I wear a mask?
In a small, enclosed shed, yes: a HEPA or N-100 respirator, per NMSU. Paper dust masks don't work.
What about mice in the well house?
Same steps. Air it out, soak and wipe, then seal the door and any pipe openings.