Mice enter storage units through small gaps, feed on cardboard and fabric, and multiply quickly in dark spaces

Mice can get into a storage unit through openings as small as a dime. Once inside, they nest in boxes, chew through cardboard and stored items, and leave droppings that damage everything around them. A single mouse can become dozens within weeks. The best defense is sealing entry points, removing food sources, and making the space inhospitable before mice arrive—not after you spot one.

Storage units are attractive to mice because they offer shelter, darkness, and often an abundance of materials to nest in. Unlike a home where you notice activity quickly, a storage unit sits undisturbed for weeks or months, giving mice time to establish a colony. Prevention is far cheaper and easier than dealing with an infestation.

Key Takeaways

  • Seal all visible cracks, gaps around the door frame, and holes in the walls with steel wool and caulk, since mice cannot chew through steel.
  • Store food items, pet food, and anything with a scent in airtight plastic containers, never in cardboard boxes or paper bags.
  • Elevate boxes off the floor using plastic shelving or pallets so mice cannot hide underneath and so you can spot droppings.
  • Place snap traps or electronic traps along the walls where mice travel, and check them every two weeks if you visit regularly.
  • Ask your storage facility whether they spray for pests and how often, since facility-wide treatment reduces the chance mice will enter your unit.

Seal cracks and gaps around the door and walls

Mice can squeeze through any opening larger than a pencil. Start by inspecting the door frame, the bottom of the door, and all corners where the walls meet. Look for gaps where light comes through or where you can see daylight. These are your entry points.

Use steel wool as your first line of defense. Mice cannot chew through it. Stuff steel wool into cracks, gaps around pipes, and holes in the walls. Then seal over the steel wool with caulk (silicone or acrylic latex) to hold it in place and block air flow. For larger gaps around the door frame, use weatherstripping tape on the sides and a door sweep on the bottom. If the door itself has damage, ask the facility to repair or replace it—this is their responsibility, not yours.

Check the seal around any pipes, vents, or electrical conduits that enter your unit. These are common entry routes. Seal them the same way: steel wool first, then caulk.

Store everything in sealed plastic containers, not cardboard

Cardboard boxes are a mouse's ideal home. They are straightforward to chew, soft for nesting, and often contain food residue or fabric. Never store items in cardboard boxes in a storage unit. Use plastic bins with tight-fitting lids instead. Mice cannot chew through rigid plastic as easily, and the seal keeps odors contained.

Pay special attention to food items, pet food, birdseed, and anything with a strong smell. These attract mice from outside the unit. Store them in airtight plastic containers on a shelf, never on the floor. Even sealed bags of flour, sugar, or cereal should go into plastic bins—mice can chew through paper and plastic film.

If you must store items in cardboard temporarily, wrap the boxes in plastic sheeting and seal the seams with tape. This is not as reliable as plastic bins, but it is better than bare cardboard. Remove the cardboard as soon as you can.

Elevate boxes and furniture off the floor

Mice hide in the space directly under boxes and furniture. By elevating everything, you remove their shelter and make it straightforward to spot droppings or damage. Use plastic shelving units, wooden pallets, or metal racks to keep boxes at least 6 inches off the floor.

This also protects your items from water damage if the floor gets wet and makes the space easier to clean and inspect. Leave gaps between boxes so air can circulate and you can see underneath. Avoid stacking boxes so high that you cannot see the top of the stack—mice will nest there.

Set traps and check them regularly

Even with prevention, a mouse may still enter your unit. Traps catch them before they multiply. Snap traps are inexpensive and effective. Place them along the walls where mice travel—they run along edges, not across open space. Bait them with peanut butter, chocolate, or nesting material like cotton balls. Check traps every two weeks if you visit the unit regularly, or every month if you visit less often.

Electronic traps kill mice when ready and are less messy than snap traps, but they cost more. Glue traps are available but cause suffering and are harder to dispose of—avoid them.

Do not use poison. Mice may die inside walls or under boxes where you cannot reach them, creating a smell that lasts for weeks. Traps are faster and cleaner.

Ask your storage facility about pest control

Many storage facilities spray for pests on a regular schedule—monthly, quarterly, or annually. Ask the manager when they last sprayed and how often they do it. Facilities that spray regularly have fewer mouse problems because the treatment kills mice and insects facility-wide, not just in your unit.

If the facility does not spray, ask whether they allow you to hire a pest control company to treat your unit. Some facilities prohibit outside contractors, while others allow it. If you hire someone, make sure they use methods that do not damage your stored items.

Keep a record of when the facility sprays and when you check your traps. This helps you spot patterns—for example, if mice appear after the spray wears off, you know the timing of the next treatment.

Remove clutter and keep the unit organized

Mice thrive in cluttered spaces where they can hide and nest unseen. Keep your unit organized so you can see everything at a glance. Store items in labeled plastic bins on shelves, not in loose piles. Leave a clear path down the middle of the unit so you can walk through and inspect for damage or droppings.

Do not store old newspapers, magazines, fabric scraps, or other soft materials that mice use for nesting. If you have items you no longer need, remove them from the unit. The less there is, the fewer places mice have to hide.

Frequently Asked Questions

What should I do if I find mouse droppings in my unit?

Mouse droppings are dark, rice-sized pellets usually found along walls or under boxes. Wear gloves and a mask, then clean the area with a damp cloth and disinfectant. Do not sweep or vacuum, as this can spread particles into the air. Check nearby boxes for damage and move them to inspect underneath. Set traps when ready if you have not already.

Can I use poison to kill mice in my storage unit?

Poison is not recommended. Mice often die in walls, under boxes, or in places you cannot reach, and the smell can last for weeks. Snap traps or electronic traps are faster, cleaner, and more effective. If you use poison, place it in a locked bait station so it does not contaminate your items.

How often should I visit my storage unit to check for mice?

Visit at least once a month to inspect for droppings, chewed boxes, or other signs of mice. If you visit less often, mice can establish a large colony before you notice. If you visit every two weeks, you can catch a problem early and set traps before damage spreads.

Will my storage facility pay for pest control if mice get in?

Most facilities are not responsible for pest control inside individual units—that is your responsibility. However, if the facility has a structural problem (a large hole in the wall, a broken door seal), they should repair it. Check your lease to see what pest control responsibilities fall on you and what fall on the facility.

Do I need to use bait in my traps?

Yes, bait increases the chance a mouse will trigger the trap. Peanut butter, chocolate, and nesting material like cotton balls or dryer lint work well. Change the bait every two weeks if the trap has not been triggered, as old bait loses its smell.