A storage unit is supposed to be a secure space where you can safely leave your furniture, books, clothing, and other personal items until you’re ready to use them again. But what happens when mold enters the equation?

Unfortunately, mold growth in storage units can happen, and it can result in hundreds or even thousands of dollars’ worth of property damage when it does. Knowing the proper protocol for preventing mold growth will help you keep your items safe and minimize the risk of losing your property due to a mold infestation.

Is mold common in storage units?

Finding mold in a storage unit isn’t common, but it happens more often than you might think. Conduct a quick online search and you’ll see that coming back to a storage unit only to find belongings covered in mold has been an unfortunate reality for many.

What causes mold in a storage unit?

1. High levels of moisture

Moisture is the #1 culprit for mold growth indoors. Because mold only needs two things to survive (moisture and an organic food source), areas with high levels of moisture are very prone to developing mold infestations.

2. Improperly storing items

Many storage unit renters blindly place all of their things in cardboard boxes to be put away, not realizing that it may not be the best material to store everything. While cardboard is a great option for dry items like books and kitchen utensils, it shouldn’t be used for clothing, shoes, umbrellas, or other fabric-based items because it can’t effectively keep out moisture or pests. Putting your belongings in the proper containers is a highly effective way to protect them from mold.

We also recommend storing all items at least a few inches away from the wall and leaving space between boxes, as this will allow air to better circulate and minimize mold risk.

How do you treat mold in a storage unit?

Let’s say you go to check on your storage unit one day and see that there has been mold growth since you moved your items in. Here’s what you should do next:

1. Locate the moisture source

Mold almost always comes from moisture, so you first need to figure out where the problem area is to resolve it. The moisture could be coming in through a crack, pipe burst, leaky ceiling, or high humidity. Identify where the moisture is coming from and correct it before attempting to remove the mold.

2. Clean up the mold

Make sure you’re prepared with goggles and rubber gloves to protect yourself when performing mold removal. First, use a wet rag to dampen the area you’re working on, as this prevents mold spores from being released into the air as you clean. Then, take a cleaning brush and soap or dish detergent to scrub away as much visible mold as possible.

Once that’s done, follow up with 1.5 cups of bleach per one gallon of water and let sit for 15 minutes to kill off any lingering mold. Repeat until the mold is completely gone and then use a fan to dry the area.

Can mold grow in climate-controlled storage units?

Mold growth in a climate-controlled storage unit is uncommon, but it does happen. The only way to surely prevent mold from growing in your storage space is to follow standard best practices when selecting a unit and moving your items in.

How to prevent and remove mold growth in your storage unit?

1. Ensure proper storage

Moisture and dirt are both held in the ground, making items kept directly on surface level more prone to developing mold. We recommend using a platform to elevate your belongings at least a few inches off the ground, as well as wrapping them in a plastic sheet to keep water out.

2. Make sure items are completely dry before storing

Like mold, moisture can rapidly spread from one item to another if not removed as soon as possible. Not only does this make it easier for existing mold to travel throughout the unit, it also increases the humidity of the space overall, leading to an increased risk of new mold growth. To reduce the likelihood of this occurring, dry your items in the sun before moving them into your storage unit. In addition to drying out excess moisture, the sun will also kill any existing mold spores on your items.

3. Keep an eye on humidity levels

Humidity levels in your storage unit should remain between 30% and 50% at all times. If humidity runs higher than this, mold growth can ensue.

We recommend checking the humidity level in your unit prior to moving in or hiring a professional to do it for you. Self-testing can be done with a relative humidity gauge, although a professional test may yield more accurate results.

4. Check your unit for pre-existing mold

If your storage unit already contains mold when you move in, it is very likely that mold will soon spread to your clothing, furniture, and other stored items. That is why it’s critical to make sure your storage space is completely mold-free prior to moving your belongings in.

Inspect your entire unit for mold growth, moisture sources, or holes and cracks that may let in water damage. Doing this will ensure that the space is safe to move into and likely to stay free of mold while your items are stored there.

5. Utilize drying agents

Silica gel and charcoal are two low-cost, effective ways to keep moisture levels at a minimum in your storage unit. The lower the humidity, the lower the chances of mold developing. You can hang silica packets in a cloth bag for effective humidity control or use a charcoal bag, which will also neutralize any odors in the unit.

Falling victim to a mold infestation in a storage unit can be devastating. In addition to losing potentially thousands of dollars in ruined items, you may also lose irreplaceable sentimental goods such as old photos and heirlooms.

Fortunately, the risk of growing mold in your storage unit can be substantially reduced by adhering to a handful of effective mold prevention and remediation tips like the ones outlined above. If you have already found mold in a storage unit you’re renting out, a professional mold remediation specialist may be able to restore some of your belongings so they’re safe to use again.