Expert Advice: How to Prevent & Remove Mould in Storage Units

Mould is the kind of problem that nobody wants to deal with, but it can creep into a storage unit surprisingly easily unless you take the proper precautions. From damaging cherished belongings to posing health risks, mould is more than just an eyesore — it’s a serious issue that requires immediate attention.

Whether you’re a first-time storage user or someone who’s had to deal with mould before, our expert guide will cover everything you need to know about preventing and removing mould in storage units. We’ll explain what causes mould, share actionable tips to prevent it and provide step-by-step advice on how to get rid of it. By the end, you’ll feel confident about keeping your storage unit — and everything inside it — safe and mould-free.

What Causes Mould in a Storage Unit?

Mould thrives in damp, poorly ventilated spaces, making storage units particularly vulnerable if not managed correctly. Understanding what causes mould to grow in the first place can help you protect your belongings.

Moisture

Moisture is the leading cause of mould in storage units, or anywhere for that matter, which is why you’ll often find it in bathrooms and kitchens. However, unless you’re cooking, washing up or showering in your storage unit, you might wonder how there’s enough moisture in your unit for mould to grow. Well, there are several ways moisture can sneak into your unit, including:

• Damp Items: Placing freshly washed clothes, wet shoes or furniture with hidden moisture into storage can introduce dampness. Even seemingly dry items may retain moisture, especially fabrics and upholstery.
• Condensation: Metal storage units, like shipping containers, can accumulate condensation when the outside temperature fluctuates significantly, creating small but persistent water droplets inside.

Pro Tip: Well-maintained shipping containers are 100% waterproof. This means they won’t only prevent water from seeping in, but will also trap it inside. Fortunately, we have another guide on How to Prevent Condensation, which will help you prevent mould growing in your unit and on your belongings.

• External Water: Rainwater, leaks, flooding and high humidity can all lead to damp conditions. Storage units located in low-lying areas or near water sources are especially at risk.

Lack of Ventilation

Without proper airflow, any moisture inside the unit becomes trapped. This stagnant air creates an ideal environment for mould spores to settle and spread, especially in tightly sealed units.

Organic Materials

Mould feeds on organic materials such as paper, fabric, wood and leather. Items like books, clothing and furniture are particularly susceptible unless they’re stored in protective packaging and treated against mould.

Temperature Fluctuations

Drastic temperature changes can create a cycle of condensation and evaporation, especially in climates with pronounced seasonal shifts. Cold nights and warm days are a common recipe for condensation inside metal units.

The Risks of Mould

Mould isn’t just unsightly — it can cause serious problems if left unchecked. Whether it’s creeping onto your belongings or lurking in the corners of your storage unit, the risks it poses could be more serious than you realise.

Damage to Your Belongings

Mould can wreak havoc on your stored items, particularly those made of organic or porous materials. Once it takes hold, it spreads quickly, often leaving your belongings permanently stained, weakened or completely unusable. Here’s how it affects common storage items:

• Clothing & Fabrics: Mould doesn’t just stain clothes, it weakens their fibres over time, making your favourite outfits and soft furnishings brittle and fragile.
• Books & Paperwork: Paper is highly absorbent, which makes it a magnet for mould. It doesn’t take long for treasured books and important files to become irreparably damaged.
• Furniture: Wooden and leather surfaces are prime targets for mould. Left untreated, mould can cause discolouration, warping and rot, particularly in damp or humid conditions.

Health Hazards

The impact of mould isn’t limited to your belongings — it can also affect your health. Mould spores spread through the air, meaning you don’t have to touch mould directly to feel its effects. For some people, exposure can trigger a range of symptoms, including:

• Allergies & Respiratory Issues: Sneezing, coughing, nasal congestion and even asthma attacks can be triggered by mould exposure. Furthermore, if you have any underlying or preexisting respiratory conditions, mould is likely to exacerbate them further.
• Skin Irritation: For anyone with sensitive skin, even brief contact with mould can lead to red and itchy rashes.
• Toxic Mould Risks: While not all mould is dangerous, certain strains, like black mould, produce toxins that can be harmful when inhaled over extended periods. If you notice a persistent musty smell or visible black spots, it’s important to address the issue promptly.

Financial Costs

As well as taking a toll on your health and belongings, mould can be a very costly issue to deal with. For example, if mould develops and spreads in your storage unit, you could face:

• Replacement Costs: Some items may be damaged beyond repair, which means you’ll need to replace them entirely. This can be particularly painful when dealing with high-value or sentimental items.
• Cleaning & Restoration Fees: Professional mould removal or item restoration can be expensive, especially for delicate and large items, such as furniture.
• Insurance Issues: Not all storage insurance policies cover mould-related damage. If the issue is considered preventable, you might find yourself footing the bill.

Recognising and understanding the risks of mould only emphasises the need to take preventative measures to stop it from growing, or work to quickly eliminate it if you find any in your storage unit.

How to Prevent Mould

Trust us, when it comes to mould, prevention is always better than cure.

As there isn’t a simple one-step solution to completely eradicate the risks of mould growing in your storage unit, we recommend implementing a few (if not all) of the tips and techniques covered in this section.

By minimising the opportunity for mould to grow in your unit, you’re maximising the chances of keeping your stored belongings safe and saving yourself the hassle of dealing with mould and the damage it may cause.

Pack Belongings Carefully

First things first, the way you prepare your items for storage plays a huge role in preventing mould. With this in mind, be sure to pack your belongings properly.

• Clean & Dry Everything: If there are two things that you should never put in storage, it’s items that are dirty or damp. While it’s important to ensure everything is clean, it’s just as important to make sure it’s dry. This is especially true if you’re storing recently washed clothes, cleaned furniture or even items exposed to rain during transit.
• Use Plastic Storage Containers: Cardboard can absorb moisture and become a breeding ground for mould, which is why we suggest using airtight plastic boxes instead.

Pro Tip: Remember, any trace amounts of moisture inside a plastic container won’t be able to escape, which is why it’s important to ensure that anything stored inside plastic containers is 100% dry.

• Protect Sensitive Items: Wrap delicate belongings like upholstered furniture or mattresses in breathable covers to shield them from dust and moisture.

Maintain Good Airflow

Ventilation plays a key role in keeping mould at bay. Stagnant air encourages damp conditions, so arranging your belongings in a way that allows air to circulate is critical. Avoid overpacking your unit or stacking items too closely together and try to create gaps between your belongings to help reduce the risk of moisture build-up.

It’s also worth considering the placement of your items. Keeping boxes and furniture directly on the floor can make them vulnerable to any residual dampness whereas elevating them on pallets (or shelves) will improve airflow and provide an extra layer of protection against water seeping from the ground.

Control Humidity Levels

Since mould thrives in humid environments, keeping the air inside your unit dry is one of the most effective preventative measures you can take. Desiccants, such as silica gel packets, are a simple and cost-effective way to absorb excess moisture. If you’re storing items for a long time or in a humid area, portable dehumidifiers can be a great way to maintain a stable environment inside your unit. Just remember to check that your unit has an electricity source before buying one.

Regularly inspecting the unit for leaks or signs of water is equally important. Pay attention to damp patches on the walls, water pooling on the floor or an unexplained musty smell — these can all be early indicators of a damp problem.

Monitor Regularly

To ensure your best-laid plans don’t go to waste, it’s always worth checking in on your unit to ensure everything is as it should be. Make it a habit to check your unit periodically, especially after heavy rain or during significant weather changes. Early detection of potential problems, like small spots of mould or dampness, allows you to address them before they escalate.

If possible, consider rotating or repacking your belongings every few months. This not only gives you a chance to spot any early signs of trouble but also ensures that no single item remains in a vulnerable position for too long.

Choose the Right Storage Unit

Knowing how to choose the best storage facility can make all the difference when it comes to mould prevention. High-quality storage units, like those made from waterproof shipping containers, offer superior protection compared to many other options. These units are designed to keep moisture out but require care to avoid trapping moisture inside.

Location is another factor to consider. Units situated in low-lying areas or places with poor drainage are more prone to flooding and other moisture issues. Ask potential providers about their unit maintenance and the drainage systems they have in place to ensure you’re using the best facilities available.

By taking these preventative measures, you can store your belongings with confidence, knowing they’ll remain safe, dry and free of mould.

How to Remove Mould in a Storage Unit

If mould has already taken hold in your storage unit, it’s important to act quickly. Left unchecked, it can spread rapidly, causing even more damage to your belongings. Fortunately, with the right approach, you can address the problem effectively and minimise the risk of it returning.

Assess the Situation

Before diving in, take a moment to evaluate the extent of the mould growth. Small patches can often be handled with DIY cleaning methods, while larger infestations may require professional assistance. If the mould has spread to multiple items or large areas of your unit, it’s worth consulting a mould remediation expert.

Gather Your Supplies

To safely remove mould — and stop it from coming back — you’ll need the right tools and cleaning products, including:

• A face mask and gloves to protect yourself from spores.
• Cleaning solutions like white vinegar, baking soda or specialised mould removers.
• Soft brushes and cloths for scrubbing.
• Airtight bags for disposing of contaminated materials.

Pro Tip: Avoid using bleach-based products on porous surfaces like wood or fabric. It may kill mould on the surface but won’t penetrate deeply enough to remove it completely.

Start Cleaning

Begin by removing affected items from the unit and placing them in a well-ventilated area. This will make cleaning easier and prevent spores from spreading to unaffected belongings. For hard surfaces, apply your chosen cleaning solution and scrub gently to remove the mould. Rinse and dry the area thoroughly to ensure no moisture is left behind.

For soft items like fabrics and upholstery, cleaning can be more tricky, so much so that we’d recommend hiring the help of a professional cleaning service. If, however, the mould is deeply embedded in the material, your items may, unfortunately, be beyond saving.

Ventilate & Dry Your Unit

Once you’ve cleaned the affected areas, it’s vital to air out the unit to disperse any remaining moisture. Open the doors and, if possible, use a fan to enhance airflow. This step helps reverse the conditions that allowed mould to grow in the first place.

Prevent Future Growth

Removing mould is only half the battle. To ensure it doesn’t return, take steps to address the conditions that caused it to begin with. Check for leaks, invest in moisture absorbers and ensure that all the items you put back in storage are both clean and dry.

Who’s Responsible for Mould in a Storage Unit?

When it comes to mould in storage units, responsibility is often a grey area. While storage providers have a duty to maintain their facilities and ensure the integrity and cleanliness of their units, they aren’t responsible for what you store, or how you store it.

If you’ve introduced moisture to your unit, perhaps by storing damp items, there’s a high chance that’s what caused mould to grow. This is why it’s so important to pack and prepare your belongings carefully before placing them in storage.

On the other hand, if your provider supplied you with a unit that was already compromised — for example, one with poor ventilation, a leak or visible signs of water damage — they may hold some responsibility. However, proving that mould growth was a result of poor facility maintenance can be tricky, particularly if the company is unwilling to cooperate.

The key takeaway? Always research your storage provider thoroughly. Choose a company that prioritises quality customer service and maintains their units to a high standard.

At Pay Less for Storage, all our units are converted shipping containers — specifically designed and built to protect valuable goods being transported across the ocean. Our units are not only waterproof but also incredibly durable, giving you peace of mind that your belongings are stored in a safe and well-maintained environment.

Does Mould Affect Storage Insurance?

Whether or not mould damage is covered by your self storage insurance largely depends on your policy. Insurance policies can vary greatly, and while some may include coverage for mould-related damage, others may exclude it entirely, especially if the damage is deemed preventable.

The key to understanding your coverage is to read the fine print. Look for clauses that mention mould, mildew, damp and water damage and note any conditions or exclusions. For example, many policies won’t cover mould if it results from negligence, such as storing damp items or failing to address leaks in a timely manner. However, if mould is caused by an issue with the storage facility itself, such as a structural defect or flooding, you may be able to make a claim.

Tips for Navigating Storage Insurance:

1. Review Your Policy: Take the time to thoroughly review your insurance policy before signing up. If anything is unclear, ask the provider for additional clarification.
2. Document Your Belongings: Keep an inventory of the items you have in storage, complete with photos and approximate values for each one. This is essential for making future claims, as you’ll need to prove the items you’re claiming for were kept in your storage unit.
3. Take Preventative Measures: Insurers may look favourably on policyholders who take reasonable steps to prevent damage, such as using moisture absorbers or packing items in airtight containers.
4. Consider Upgrading Your Coverage: If your current policy doesn’t cover mould, ask your provider if additional coverage is available. The extra cost could be worth the peace of mind.

Ultimately, mould can be unpredictable, and having comprehensive insurance offers an added layer of protection for your belongings. While prevention is always the best strategy, knowing you’re covered can make all the difference if the unexpected happens.

FAQs

Is mould common in storage units?

Mould can develop in storage units, but it’s usually the result of moisture or poor preparation when storing items. Choosing a well-maintained unit and following proper storage practices significantly reduces the risk of mould damaging your stored belongings.

How do you get mould out of a storage unit?

To remove mould, clean affected areas with solutions like white vinegar or specialised mould removers — and be sure to dry them thoroughly to prevent it from growing back.

How to prevent mould in a storage unit?

Prevent mould by ensuring all items are clean and completely dry before storing, improving ventilation and using moisture absorbers or dehumidifiers in your unit. Regular inspections and choosing a high-quality storage unit may also help prevent mould from growing in the first place.

Is mould from moisture toxic?

Some moulds can produce allergens or toxins that pose health risks, particularly to those with respiratory conditions or allergies. While not all mould is toxic, it’s still important to address it promptly.

Are storage units responsible for mould?

Storage providers are responsible for maintaining their facilities, but they’re not liable for mould caused by stored items or how they’re stored. Always check the condition of your unit before signing a contract and follow proper storage practices and techniques to prevent issues.