Mice in a Storage Unit: How to Keep Them Out and Protect Your Belongings

TL;DR

• Pick the right facility first: a regular pest control program, tight door seals and clean grounds. It's the single biggest thing you can do as a renter.
• Store no food in the unit, not even unopened, non-perishable items. That includes pet food and bird seed.
• Pack in hard plastic bins with tight lids instead of cardboard. They aren't always mouse-proof, but they usually protect your things better.
• Keep everything off the floor on metal shelving or clean pallets, and leave an aisle so you can see the floor and corners on every visit.
• Check the unit regularly for droppings and chewed boxes. Skip mothballs: repellents usually do not keep mice out of a storage unit on their own.
• Need help? Get a quote from a recommended local exterminator through Pest Agent's referral form.

Mice in a storage unit tend to reveal themselves at the worst moment: you roll up the door after months away and find chewed boxes, droppings on a mattress and a nest in the sofa you meant to keep. By then they have had all season to work through your cardboard, fabric and paper.

The choices that prevent that scene are made before the door is locked: which facility you rent from, what goes into each container and how everything sits in the unit.

A unit nobody opens for months, stacked with boxes and soft furniture, offers mice almost everything they look for in a place to nest.

Why Do Mice Get Into Storage Units?

Mice get into storage units because units are quiet, rarely visited and full of cardboard, fabric and paper they can nest in. A storage building can also give them shelter from the cold, and the belongings inside can hide a nest for months before anyone notices.

Quiet, Undisturbed Space

A storage unit is quiet and often goes unchecked for long periods, which can make it what Abell Pest Control describes as an ideal home for rodents. Mice are most active at night (UC IPM), and in a unit nobody visits, they can move, feed and nest without being disturbed. According to UC IPM, mice that have few places to hide, rest and build nests generally cannot survive in large numbers, so a packed, cluttered unit can give them what they need.

Nesting Material

Nesting material is everywhere in a typical storage unit. House mice build their nests from finely shredded paper or other fibrous material, and UC IPM suggests searching behind boxes and in drawers to find them. Cardboard boxes, stored clothing, paper files, mattresses and upholstered furniture are all easy to shred. Some pest control companies also list soiled clothing, scented candles, potpourri and deodorant among the items that draw rodents in.

Food Brought In by Tenants

Food brought in by tenants is how many storage infestations start. A self-storage industry publication notes that flour kept in an unsealed bag can attract rodents. Even slight food residue on a frying pan or a baking dish may be enough, according to Abell Pest Control, and pet food and bird seed are frequent culprits.

Gaps Under Doors and Between Units

Gaps under doors and between units let mice move in and around a storage building. Health Canada says mice can squeeze through cracks as small as a dime, and UC IPM gives openings as small as 1/4 inch (about 6 mm). Missing door sweeps can be a common way mice get into units. Most self-storage lockers are not completely sealed, so mice can travel from one unit to the next, and they can also arrive inside furniture or boxes that another tenant moves in.

Autumn and Winter in Canada

Autumn and winter bring more mice indoors in Canada. UC IPM notes that house mice often move into buildings in autumn as nights get colder, and Health Canada says deer mice may invade buildings near fields and woodlands in the fall. A storage facility on the edge of town, next to fields or trees, may see a rise in mouse activity from late fall onward. The same seasonal pattern affects sheds and garages.

How Do You Know if There Are Mice in Your Storage Unit?

Mice in a storage unit leave droppings, chewed boxes and shredded nesting material long before you see a mouse. Check the floor along the walls, the corners and the tops of boxes each time you visit.

Droppings

Droppings are the clearest sign. Mouse droppings are typically about 1/8 to 1/4 inch (about 3 to 6 mm) long, dark and often shaped like grains of rice. You usually find them along walls, on top of boxes and inside drawers. Do not sweep or vacuum them: Health Canada warns that the dust raised by dry droppings can cause illness.

Chewed Boxes

Chewed boxes show where mice are feeding or collecting nesting material. Look for small holes in the corners of cardboard boxes, ragged edges, chewed fabric on furniture and damaged books or papers. Gnaw marks are one of the signs Health Canada lists for rodent activity.

Nests

Nests look like a loose ball of shredded paper, fabric or insulation. In a storage unit, check inside drawers, under sofa cushions, inside mattresses and box springs, and in the gaps between stacked boxes.

Musky Smell

A musky smell is often associated with mice, especially in long-term infestations (UC IPM). In a closed unit, the smell of urine can build up into a sharp, ammonia-like odour. If your unit smells stale or musky when you open the door, look closely for the other signs. For a broader checklist, see our guide to the signs of a mouse infestation.

How to Choose a Storage Facility That Keeps Mice Out

A storage facility that keeps mice out has a regular pest control program, tight door seals and clean grounds. Since you rent the unit and cannot repair the building yourself, choosing the right facility is the single biggest thing you can do.

Pest Control Program

A pest control program is the first thing to ask about. Some storage operators recommend looking for regular pest control, such as monthly or quarterly. Abell Pest Control describes a typical self-storage program in Canada with regular visits, traps or bait stations inside and locked bait stations outside, and Health Canada says poisoned baits must be used in a tamper-proof bait station in areas accessible to children and pets. Individual units are usually inspected only on request, for privacy and security reasons, so ask whether the facility will have its pest control company check your unit if you see signs of mice.

Door Seals

Door seals tell you a lot about how a facility is maintained. Before you sign, look at the bottom of your unit door: the sweep should touch the floor along its full width, with no daylight showing. Remember that a mouse can fit through a gap the size of a dime. Check the walls, corners and ceiling of the unit for holes, and look for droppings or torn paper on the floor.

Clean Grounds

Clean grounds mean fewer mice near the buildings. Look for well-kept landscaping, no trash along the borders of the property, closed garbage bins and frequent garbage pickup. Tall weeds, piled debris or overflowing dumpsters near the units are a warning sign.

Rental Contract

Your rental contract decides who handles a mouse problem. Ask what the facility's infestation policy is, whether it has had rodent problems, and what you are allowed to store. Read the contract closely, because some facilities may waive responsibility for rodent damage. In general, the facility is expected to maintain the building and keep pests from getting in, while you are responsible for what you bring and how you store it. Check what your insurance covers too.

Is Climate-Controlled Storage Mouse-Proof?

Climate-controlled storage is not mouse-proof. It regulates heat and humidity, but it does not seal the unit: ventilation ducts, loading dock doors, floor drains and pipe gaps can still let mice in, according to some pest control companies that service storage facilities. Stable temperatures may even make these buildings more attractive in cold months. Climate control can still be worth it for items that suffer from heat or humidity, but pack with the same care.

Portable Storage Containers

Portable storage containers can be a good option when you want a tighter seal. Some container companies, such as BigSteelBox, describe their shipping containers as rodent proof, with rubber gaskets along the doors. That is the operator's own claim, so inspect the door gaskets yourself and pack the container exactly as you would a unit. Mice that are already inside furniture or boxes will travel in with them.

How to Keep Mice Out of a Storage Unit When You Pack

Keeping mice out of a storage unit starts with packing: nothing to eat, nothing easy to chew, and nothing on the floor. These steps cost little and protect your belongings for as long as they stay in storage.

No Food

Store no food in your unit, not even unopened, non-perishable items. That includes canned and dry goods, pet food, bird seed and live plants. Many facilities restrict food in their rental contracts, and a single forgotten bag can draw mice from the whole building. At home, Health Canada recommends keeping dry food and dry pet food in metal or glass containers.

Plastic Bins Versus Cardboard

Hard plastic bins with tight lids protect your things better than cardboard, but they are not mouse-proof. UC IPM notes that mice can chew on storage containers meant to keep them out, and one trap manufacturer says plastic bins may only slow rodents down. Still, a sealed bin gives mice no easy way in and no loose material to shred. If you use cardboard, choose new, sturdy boxes, tape every seam and avoid used boxes from grocery stores or restaurants. Keep clothing, linens and paper in sealed bins or bags.

Clean Items Before Storage

Clean items before storage so nothing smells like food. Wash pots, pans, dishes and small appliances, empty and wipe out fridges, and vacuum crumbs out of sofas and chairs. Check furniture for droppings, chew holes and nests before you load it, especially second-hand pieces, so you do not bring mice or bed bugs into the unit with you.

Covered Furniture

Covered furniture is harder for mice to reach and easier to inspect. Wrap mattresses in plastic mattress bags. For sofas and fabric chairs, some storage companies suggest breathable covers, because tight plastic wrap may trap moisture. Avoid wrapping anything that is still damp.

Keep Items Off the Floor

Keeping items off the floor makes it harder for mice to hide and nest. Put boxes on metal shelving or clean pallets, and use hooks or hanging bags for clothing.

Leave an Aisle

Leaving an aisle down the middle of the unit and a little space along the walls lets you see the floor and corners on every visit. A unit packed solid from wall to wall hides droppings, gives mice a protected path, and makes an infestation much harder to find and clean up.

How to Keep a Storage Unit Mouse-Free Over Time

A storage unit stays mouse-free when you check it regularly and catch the first mouse early. Mice breed fast: according to UC IPM, a female house mouse may have many litters in a year, with several young each time.

Regular Visits

Regular visits are your early warning system. One storage operator suggests checking your unit about every other month, and a visit after the first cold weeks of fall is a good habit in Canada. Each time, look along the walls and in the corners for droppings, check box corners for chewing, and report any holes or damaged door seals to the facility.

Traps

Traps are a safe way to catch the first mouse early, but ask the facility before you set any. Health Canada says snap traps and electronic traps are very effective when well positioned and set properly. Set them along the walls, about 1 trap per metre, and bait them with a strong-smelling, sticky food such as peanut butter. Avoid glue traps and live traps: the CDC advises against them, and UC IPM notes that live traps quickly become contaminated with mouse feces and urine, and that releasing mice elsewhere often does not work. Since you may only visit every few weeks, a dead mouse in a closed unit will smell, so check traps on every visit. Our guides on how to set a mouse trap and the best mouse traps can help you choose.

Bait Stations

Bait stations with poison are best left to the facility and its pest control company. Some facilities do not allow tenants to use poison, and a mouse that eats bait can die inside your boxes or furniture, where the smell is hard to remove. In Canada, domestic poison baits generally have to be used in a tamper-proof bait station, and the Government of British Columbia restricts the sale and use of second-generation anticoagulant rodenticides. Any product you use must have a PCP number on the label, which shows it has been approved by Health Canada.

Repellents

Repellents do not keep mice out of a storage unit on their own. An extension expert from the University of New Hampshire says repellents, whether mothballs, essential oils or other home remedies, have not proven very effective, because their scent tends to fade quickly. Skip mothballs entirely: they should not be used to repel mice unless the label describes that use, their vapours can irritate your eyes and nose, and storage operators warn that the smell can damage clothing and furniture in neighbouring units too. Health Canada adds that mice may adapt to ultrasonic devices. For an overview of what works and what does not, see our review of mouse repellents.

What to Do if You Find Mice in Your Storage Unit

If you find mice in your storage unit, tell the facility first, then clean up safely before you sort anything. Moving fast keeps the problem from spreading to your other belongings or to neighbouring units.

Tell the Facility

Tell the facility manager right away, and take photos of the droppings, damage and any holes or gaps you find. The facility is responsible for the building and its pest control program, and it needs to know so it can check the units around yours. Ask whether its pest control company can inspect your unit.

Safe Cleanup

Safe cleanup matters because mouse droppings, urine and nests can carry germs, and the deer mouse is the most common carrier of hantavirus in Canada, according to Health Canada. Follow the steps from the Public Health Agency of Canada and Alberta Health:

1. Open the door and let the unit air out for at least 30 minutes before you start.
2. Wear rubber or plastic gloves, and in a confined space like a storage unit, wear an N95 respirator.
3. Do not sweep or vacuum droppings or nests.
4. Spray them with a Health Canada-approved disinfectant or a mix of 1 part bleach to 9 parts water (Health Canada advises a bleach and water solution), and let it soak for about 10 minutes.
5. Wipe everything up with paper towels, double-bag the waste and throw it out according to your local by-laws.
6. Wash your gloves before taking them off, then wash your hands.

For a heavy infestation, PHAC suggests considering a professional cleaning company, and in Alberta you can call Health Link 811 for advice. Our step-by-step guide on how to clean mouse droppings covers the details.

Check Items Before Bringing Them Home

Check every item before bringing it home, so you do not move the mice into your house. Open boxes in the unit or outdoors, look inside drawers, cushions and mattresses for nests, and throw out anything heavily soiled with droppings or urine. Do not carry boxes straight into your home until they have been inspected and cleaned. Our guide on how to keep mice out of your house explains how to protect your home afterward.

When to Call a Professional

Calling a professional makes sense when you find many droppings, several nests, or mice keep coming back after the facility has acted. The facility's own pest control company is the first call. If you are moving the belongings home and want your house checked, a licensed pest control professional can inspect and treat it, and you can get a quote from a recommended local exterminator through Pest Agent's referral form. You will find more mouse guides on our mice hub.