Mice enter storage units through gaps smaller than a dime and breed fast in dark spaces full of cardboard and fabric

Mice can squeeze through openings as small as one-quarter inch and will nest in stored boxes, blankets, and insulation within days of arrival. Once inside, they reproduce quickly—a single female can have five to ten litters per year—and their droppings carry disease. The best defense is prevention: seal entry points, store food and scented items outside the unit, and use traps or bait stations before an infestation takes hold.

Storage units are ideal mouse habitats because they offer shelter, darkness, and often a steady supply of nesting material. Unlike a home where you notice activity right away, a storage unit sits undisturbed for weeks or months, giving mice time to establish a colony undetected. The combination of temperature swings, humidity, and neglect makes even a clean unit vulnerable.

Key Takeaways

  • Seal all gaps, cracks, and holes around doors, vents, and utility penetrations with steel wool and caulk, since mice cannot chew through steel.
  • Store all food, pet food, birdseed, and scented items (candles, spices, soap) outside the unit or in airtight metal containers, as these attract rodents.
  • Keep boxes off the floor on plastic shelving or pallets, and use plastic storage bins instead of cardboard whenever possible.
  • Set snap traps or electronic traps along walls and in corners where mice travel, and check them every two weeks during the rental period.
  • Request that your facility inspect the unit's door seal and exterior for damage, and report any gaps to management when ready.

Seal Entry Points Before You Move In

Inspect the unit's door frame, bottom seal, and all corners for gaps, cracks, or damage before you bring anything inside. Mice need only a quarter-inch opening, so look closely at where the door meets the frame, where the frame meets the wall, and around any vents or utility lines. If the door does not close flush or the rubber seal is cracked, ask the facility to repair it—this is often a management responsibility.

For gaps you can address yourself, use steel wool as your primary barrier. Mice cannot chew through steel, unlike plastic or rubber. Stuff steel wool tightly into cracks and holes, then seal over it with silicone caulk or expanding foam. Pay special attention to the bottom corners of the door, where the frame meets the concrete floor, and any penetrations for electrical outlets or pipes. Do not rely on caulk alone; the steel wool backing makes it effective.

Check the door's weatherstripping and bottom seal regularly. Concrete floors settle and shift, and door frames can warp, creating new gaps over time. If you rent the unit for more than a few months, inspect it again halfway through your rental period.

Remove Food and Scented Items That Attract Mice

Mice are drawn to food, pet food, birdseed, and strong smells. Do not store any of these in your unit, even in sealed bags—rodents can smell them through packaging and will chew their way in. This includes pantry staples like flour, sugar, cereal, nuts, and dried fruit. Move these items to your home or a climate-controlled pantry elsewhere.

Scented items also attract mice: candles, essential oils, spices, dried herbs, soap, and perfume all trigger their curiosity. If you must store spices or cooking ingredients, transfer them to airtight metal containers with tight-fitting lids. Plastic containers are not sufficient—mice can gnaw through them. Glass jars with metal lids work if the seal is truly airtight.

Pet food and birdseed are especially problematic. Even a small bag left in a corner will draw mice from outside the unit. If you store pet supplies, keep them in metal bins with locking lids, and store the bins in a separate location if possible. The same rule applies to any dried goods: metal containers with find seals, or store them elsewhere.

Use Plastic Bins and Shelving to Reduce Nesting Sites

Cardboard boxes are ideal nesting material for mice. They tear easily, hold warmth, and break down into soft fibers. Replace cardboard storage with plastic bins whenever you can. Plastic bins are harder for mice to chew through, easier to clean if droppings appear, and stack more securely than boxes.

Keep all storage at least six inches off the floor using plastic shelving units or wooden pallets. Mice travel along walls and under items on the ground; elevating your belongings makes it harder for them to hide underneath and nest. Avoid stacking boxes directly on concrete, and do not let items touch the walls—leave a few inches of clearance so you can see if mice are nesting behind them.

Wrap items that cannot go in plastic bins—such as furniture, clothing, or bedding—in plastic sheeting or plastic storage bags. Mice will chew through fabric and paper, but plastic is a barrier. Seal the wrapping with tape so it does not come loose. Avoid using newspaper or cardboard as padding; use bubble wrap or plastic instead.

Set Traps and Bait Stations Before Mice Arrive

Place snap traps or electronic traps along the walls and in the corners of your unit, especially near the door and any gaps you have sealed. Mice follow walls as they move, so position traps perpendicular to the wall with the trigger facing the wall. Bait them with peanut butter, chocolate, or nesting material like cotton balls. Check traps every two weeks during your rental period, even if the unit appears empty.

If you prefer not to handle dead mice, use electronic traps that kill on contact and hold the body in a sealed chamber, or use bait stations with rodent poison. Bait stations are tamper-resistant boxes that allow mice to enter but keep the poison away from pets and children. Place them along walls where you see droppings or signs of activity. Follow the product instructions for placement and frequency of checks.

Do not use glue traps. They are inhumane and often fail to kill the mouse quickly. Snap traps and electronic traps are faster and more reliable. If you use poison, dispose of dead mice in a sealed bag in an outdoor trash bin, and wear gloves when handling them.

Monitor for Signs of Mice During Your Rental Period

Visit your unit every two to four weeks to check for droppings, chewed boxes, or nesting material. Mouse droppings are small, dark, and rod-shaped—about the size of a grain of rice. Fresh droppings are soft and dark; older ones are hard and gray. Droppings near boxes, in corners, or along walls indicate active mice.

Look for chewed cardboard, shredded paper, or holes in plastic bins. Mice also leave greasy rub marks along walls and baseboards where their fur touches repeatedly. If you find any of these signs, set additional traps when ready and consider asking the facility to inspect the unit for new entry points. Mice may have entered through a gap you missed or through a damaged door seal that has worsened.

If you discover an active infestation—multiple droppings, visible nesting, or live mice—contact the facility's management right away. Many storage facilities have pest control contracts and can treat the unit professionally. Do not attempt to clean up a large infestation yourself; mouse droppings can carry hantavirus, which spreads through dust when droppings are disturbed.

Work with Your Storage Facility on Pest Prevention

Ask your facility whether they conduct regular pest inspections or have a pest control contract. Some facilities spray units between rentals or maintain bait stations in common areas. Understanding their practices helps you know what additional steps you need to take.

Report any damage to the unit's door, frame, or seal to management in writing. A broken door seal or gap in the frame is the facility's responsibility to repair, and fixing it protects all tenants. If the facility is slow to respond, document the damage with photos and follow up in writing again. A sealed, well-maintained unit is your first line of defense.

If mice appear despite your precautions, ask whether the facility will treat the unit at no charge or share the cost. Many facilities will, especially if the infestation is due to a structural problem like a damaged door. Keep records of any pest activity and the steps you have taken, in case you need to dispute a damage claim later.

Frequently Asked Questions

Can I use mothballs or ammonia to keep mice away?

Mothballs and ammonia have a strong smell that may deter mice temporarily, but they are not reliable. Mice will tolerate the smell if food or nesting material is available, and the odor fades over time. Sealing entry points and removing attractants are far more effective. Mothballs also release toxic fumes in enclosed spaces, so use them only if the unit is well-ventilated.

What if I find a dead mouse in my unit?

Wear disposable gloves and place the mouse in a sealed plastic bag, then dispose of it in an outdoor trash bin. Do not touch your face or eat before removing the gloves. Wipe the area with a damp cloth or disinfectant spray. If you find multiple dead mice or a strong odor suggesting a hidden carcass, contact the facility's management for professional cleanup.

Do ultrasonic mouse repellents work?

Ultrasonic devices claim to repel rodents with high-frequency sound, but scientific studies show they are ineffective. Mice quickly become accustomed to the noise, and the devices do not prevent entry or remove food sources. Save your money and focus on sealing gaps and removing attractants instead.

How often should I check my traps?

Check traps every two weeks at minimum, more often if you see signs of mice. A trapped mouse can attract other mice and create odor problems if left too long. If you visit the unit less frequently than every two weeks, consider bait stations instead, which require less frequent monitoring.

Can mice chew through plastic storage bins?

Mice can chew through thin plastic, but it takes effort and time. Heavy-duty plastic bins are much harder for them to penetrate than cardboard. Combine plastic bins with elevated shelving and sealed food storage, and the risk drops significantly. If you see bite marks on a bin, move its contents to a metal container or inspect the unit for new entry points.