Late winter is when many gardeners open the shed for the first time in months and find chewed seed packets, a nest in the potting soil bag, or droppings across the workbench. Knowing how to keep mice out of shed spaces matters most right now, before you start hauling out seed trays, cushions, and tools for spring.
This guide covers how to clean up safely if mice spent the winter in your shed, how to seal it and set it up so they do not move back in, and how the same steps apply to a rented storage unit.
The Short Answer
Air the shed out and clean up droppings the CDC way, never by sweeping. Then seal gaps under the door, along the floor, and around vents, move seed and feed into sealed metal or heavy plastic containers, replace cardboard with plastic bins, and clear the cover around the outside. A scent repellent can add a layer near the door and in corners once the shed is sealed.
Why Mice Love Garden Sheds
The National Pest Management Association (NPMA) says deer mice seek shelter in homes, garages, sheds, and rarely used vehicles during winter. Outdoors, the NPMA notes they nest in log piles, fence posts, and beneath decks, which describes the area right around many sheds.
A shed sits quiet for months and often holds seed, cardboard, rags, and cushions. The University of California Integrated Pest Management Program (UC IPM) lists wood among the gnawable materials that do not work for plugging mouse holes, which matters in a wooden shed.
Step 1: Clean Up Safely Before You Start Spring Work
If you see droppings or nests, do not grab a broom. The CDC has specific steps for sheds, outbuildings, and cabins:
- Open all doors and windows for 30 minutes before cleaning, and leave the area during that time.
- Put on rubber or plastic gloves.
- Do not sweep or vacuum droppings, urine, or nesting material.
- Spray them with a bleach solution (1.5 cups of household bleach per gallon of water) or a disinfectant, let it soak for 5 minutes, and wipe up with paper towels.
- Mop hard floors, or spray dirt floors with disinfectant.
- Move stored boxes outside to a well-ventilated area, and throw away cardboard boxes soiled with urine or droppings.
- If you are working outdoors, stay upwind so dust does not blow toward your face.
How to Keep Mice Out of Shed Spaces: Step by Step
Step 2: Find the Gaps
According to the CDC, mice can fit through a hole the width of a pencil, about 1/4 inch. On a shed, check the bottom of the door, the corners where walls meet the floor, any gap between the floor and the foundation or blocks, vents, windows, and spots where wood has rotted or been chewed. The CDC specifically recommends sealing outbuildings and garages, not only the house.
Step 3: Seal With Materials Mice Cannot Chew
The CDC recommends steel wool held in place with caulk or spray foam for small holes, and hardware cloth, metal sheeting, or cement for larger openings. UC IPM warns that plastic screening, rubber, vinyl, foam, and wood are gnawable and do not work on their own. Hardware cloth over vents keeps airflow while blocking mice. If the door has a gap at the bottom, add a sweep or a metal threshold so it closes tightly.
Step 4: Store Seed and Feed Like Mice Are Watching
The NPMA advises against storing pet food or bird seed in garages or sheds. If you keep grass seed, bird seed, or animal feed in the shed anyway, the CDC recommends sealed plastic or metal containers for grain and animal feed. Paper seed packets and open bags are easy targets, so put them in a tight-lidded bin too.
Step 5: Replace Cardboard and Get Things Off the Floor
The NPMA recommends resealable plastic containers instead of cardboard boxes, and keeping stored items off the floor. Bring cushions, tarps, and fabric items home for the winter, or bag them in sealed bins.
Step 6: Clear the Outside
The CDC recommends trimming brush, weeds, and grass near the home and keeping woodpiles raised at least one foot off the ground and well away from the house. The same thinking helps a shed: keep grass short around it, do not stack firewood against its walls, and keep compost and bird feeders at a distance.
Step 7: Trap and Check
The CDC recommends snap traps and advises against glue traps and live traps, and it lists outbuildings among the places to set them. Keep traps where pets and children cannot reach, and check the shed every couple of weeks until you are sure it is clear.
Keep Mice Out of Storage Unit Spaces Too
A rented storage unit is a shed you visit even less often. The same rules apply:
- Never store food, pet food, or seed in a storage unit.
- Use lidded plastic bins instead of cardboard boxes, and keep items on shelves or pallets off the floor.
- Wrap upholstered furniture and mattresses in plastic.
- Check the unit when you visit for droppings and chewed packaging, and tell the facility manager if you see signs.
- Ask the facility what you are allowed to place in the unit before setting traps or repellents.
When to Call a Professional
Call a licensed pest control professional if you find heavy droppings or several nests, if activity continues after you have sealed and trapped, or if mice seem to be moving between the shed and your house.
Cheat Sheet
- Air the shed out for 30 minutes before cleaning. Never sweep or vacuum droppings.
- Seal gaps of 1/4 inch or more with steel wool plus caulk, or with metal and hardware cloth.
- Give the door a tight fit with a sweep or metal threshold.
- Keep seed and feed in sealed metal or heavy plastic containers.
- Swap cardboard for lidded plastic bins and use shelves.
- Keep grass short and woodpiles away from the shed walls.
- Storage units: no food, no cardboard, nothing on the floor.
Where BioGuard Fits
We sell BioGuard Natural Rodent Repellent, a pack of 12 scent balls infused with peppermint and cinnamon essential oils. Sheds, storage areas, and garden edges are among the places it is made for. Place it in corners, near the sealed door, and on shelves near stored items. It is a repellent, not a removal product, and it works best after cleanup and sealing. Replace it every 4 to 6 weeks, or sooner after heavy rain if used outdoors, keep it away from children, pets, and food, and expect results to vary.
Frequently Asked Questions
Why are there mice in my shed?
Sheds are quiet, sheltered, and often full of seed, cardboard, and fabric. Deer mice look for exactly this kind of spot in winter, and a small gap under the door is enough to get in.
Can I sweep up mouse droppings in my shed?
No. The CDC advises against sweeping or vacuuming droppings or nests. Air the shed out for 30 minutes, then wet everything with disinfectant and wipe it up with paper towels while wearing gloves.
How do I keep mice out of my garage as well?
The same logic applies, with extra attention to the door into your house. See our guide on how to keep mice out of your garage.
Are natural repellents worth using in a shed?
They can add a layer once the shed is sealed, but none replace sealing. Our guide to natural mouse repellent options covers what has a basis and what does not.
Sources
- CDC, How to Clean Up After Rodents (sheds, outbuildings, and cabins)
- CDC, How to Seal Up to Prevent Rodents
- CDC, How to Trap Up to Control Rodents
- UC IPM, Pest Notes: House Mouse
- NPMA, Deer Mice
- NPMA, Pests in the Garage (plastic containers, items off the floor)