How to Prevent Mould in Storage Units
If you have ever opened a storage box only to be hit by that damp, musty smell, you already know how mould can ruin your belongings. It does not take much for mould to grow in your storage unit. A little moisture, a bit of warmth, and something organic to cling to, and suddenly your favourite items are covered in spots you cannot scrub off.
The good news is that mould is avoidable. With the right approach, you can keep your storage unit fresh, dry, and completely mould free, even during long-term storage. Whether you are storing furniture, clothes, electronics or documents, here is how to keep mould from becoming your biggest storage problem.
Choose the right storage unit from the start
Not all storage units are equal when it comes to protecting your things. If mould is a concern, start by choosing a unit that offers the right conditions. Look for facilities that are clean, dry and well ventilated. If your items are valuable or especially sensitive, consider a climate-controlled unit. These keep humidity and temperature levels stable, which makes it much harder for mould to form.
If you are using a regular unit, pick one that is not directly exposed to water sources like drains or leaky gutters. Ground floor units can sometimes be more vulnerable to damp, so ask about ventilation and whether the building has a good moisture barrier underneath.
Pack your items when they are completely dry
It sounds simple, but it is one of the biggest causes of mould in storage. People pack damp clothes, just-washed dishes, or even wet outdoor gear without letting it dry fully first. That moisture gets trapped, and over time it creates the perfect environment for mould.
Before storing anything, give it a proper clean and let it dry thoroughly. This is especially important for things like tents, shoes, towels, mattresses and furniture with fabric. Even a little leftover moisture from a mop or sponge can do damage if it is locked in for weeks or months.
Let air move freely inside your unit
One of the best ways to prevent mould is to keep air flowing. A sealed, over-packed unit traps moisture and makes it easy for mould to take hold. Instead of pushing everything against the walls and stacking boxes right to the ceiling, leave a bit of space for air to circulate.
Raise items slightly off the ground using pallets or boards to stop cold air and moisture from creeping up through the floor. If you are storing sofas, chairs or mattresses, stand them upright and leave a gap between each item. The more air that moves around your belongings, the harder it is for damp to settle in.
Avoid plastic wrap on certain materials
Plastic seems like a safe way to protect things in storage, but it can actually cause mould if used the wrong way. Wrapping items like mattresses, fabric chairs or wooden furniture in non-breathable plastic can trap moisture inside and encourage condensation.
Instead, use fabric covers or breathable mattress bags. These still protect your items from dust and dirt but allow air to pass through, helping to prevent mould. If you do use plastic, keep it loose and only wrap items that are already completely dry and unlikely to trap moisture.
Use moisture absorbers to stay ahead of damp
If you are storing your items for more than a few weeks, it is worth adding moisture absorbers to your unit. These come in the form of silica gel packs, hanging dehumidifier bags, or refillable tubs that pull excess moisture from the air. You can place them inside boxes, drawers or just around the unit.
They are especially useful during colder months or if your unit is not climate controlled. Keep an eye on them during regular visits and replace them when they are full. A few small packets can make a big difference in protecting clothes, documents and electronics.
Check your storage unit regularly
If you live nearby, it is worth visiting your unit every few weeks to make sure everything is dry and in good condition. A quick check for any signs of mould, damp patches or odd smells can help you spot problems early before they spread.
Open a few boxes, check behind larger furniture pieces and give the unit a quick air-out if you can. If the weather is particularly humid or cold, these visits are even more important.
Clean everything before storing it
Dirty items attract mould faster than clean ones. Dust, oils and food particles provide fuel for mould spores, especially on fabric and wood. Wipe down furniture with a mild cleaner, vacuum soft furnishings and wash clothes before packing them away.
Make sure all boxes are clean too, especially if you are reusing ones from a loft or garage. Cardboard can hold moisture if it has already been exposed to damp conditions.
Keep paper and fabric off the floor
If you are storing things like books, bedding or clothing, never place them directly on the ground. The floor of a storage unit can get cold and even slightly damp depending on the season. Use plastic tubs with sealed lids or store boxes on raised platforms.
If you are keeping photos, artwork or important paperwork in storage, use airtight containers and add silica gel packs inside. For long-term storage, you can also wrap documents in acid-free paper to keep them safe from moisture and age damage.
Mould prevention is easier than mould cleanup
Once mould takes hold, it is hard to reverse. It stains, it smells, and in many cases it causes permanent damage. But the good news is that most mould issues are completely preventable with a bit of prep.
Dry your items properly, pack with airflow in mind, choose the right materials and check on your unit now and then. These small steps can save you a lot of hassle and expense later down the line. Whether you are storing your things for a month or a year, keeping mould out means your stuff will be exactly as you left it.
