How to Prevent Mold and Mildew in Boat Storage

Josh Summerhays • December 15, 2025

Mold and mildew are common issues that boat owners face when storing their vessels, especially during the off-season. These fungi thrive in damp, warm environments, making boats the perfect breeding ground if not stored properly. At Simply Storage Idaho, we understand how important it is to keep your boat in top condition, so we’ve put together some essential tips to help prevent mold and mildew while your boat is in storage.


1. Clean Your Boat Thoroughly Before Storing It


Before storing your boat, give it a deep clean to remove any dirt, grime, and moisture that could contribute to mold and mildew growth. Clean both the interior and exterior, including:


  • Hull: Wash the exterior with a boat-safe cleaner.
  • Cabin & Compartments: Wipe down all surfaces inside the boat, including seating, floors, and storage areas.
  • Upholstery & Fabrics: Clean cushions, carpets, and any fabric surfaces. You can use a mildew-resistant spray for extra protection.


Cleaning your boat before storage removes any potential moisture or organic matter that mold and mildew thrive on.


2. Dry Everything Completely


Moisture is the primary cause of mold and mildew, so it’s vital to ensure that all surfaces are dry before storing your boat. Check for any standing water in compartments, bilge areas, or on the deck. Use towels, fans, or a wet/dry vacuum to remove any remaining moisture from the boat.


Additionally, keep your boat’s canvas covers and upholstery dry before storage. Even a small amount of moisture trapped in fabric can lead to mold and mildew growth.


3. Use Dehumidifiers or Moisture Absorbers


Dehumidifiers are an excellent way to maintain a dry environment inside your boat, especially if you're storing it for long periods. There are portable dehumidifiers available for boats, or you can use moisture-absorbing products like silica gel packs or desiccants. These can be placed inside the cabin and other areas where moisture tends to accumulate.


These products help absorb excess humidity, reducing the chance of mold and mildew growth.


4. Keep Vents Open


Proper ventilation is crucial to prevent mold and mildew buildup in boat storage. Make sure all vents are open to allow air circulation inside the boat. This airflow helps prevent moisture buildup by allowing damp air to escape. If your boat has vents that can be adjusted, make sure they are in the open position during storage.


If your boat is stored indoors, consider using a fan to increase air circulation and maintain a dry environment.


5. Use Mold-Resistant Products


Mold-resistant sprays and coatings can provide an extra layer of protection against fungi. These products are available for fabrics, wood, and other materials commonly found inside boats. Apply a mold and mildew-resistant spray to your upholstery, curtains, and other fabric surfaces before storing your boat.


For wooden areas, use a mold inhibitor to help prevent moisture from causing damage over time.


6. Store Your Boat in a Dry, Climate-Controlled Area


The ideal storage solution for preventing mold and mildew growth is a dry, climate-controlled environment. At Simply Storage Idaho, we offer secure, clean, and dry storage spaces for your boat. Storing your boat in a climate-controlled unit will help regulate humidity levels, reducing the risk of mold and mildew.


If you’re storing your boat outdoors, use a high-quality cover to protect it from rain and moisture, and make sure the boat is on a dry, raised surface to prevent water from accumulating around the base.


A quality boat cover also plays a big role in moisture control, especially when storing outdoors for extended periods.


7. Regularly Check on Your Boat


If possible, periodically inspect your boat during storage to ensure that no mold or mildew has started to form. Look for signs of moisture buildup, unpleasant odors, or visible mold spots. The earlier you spot potential problems, the easier it will be to take action before the issue worsens.


Preventing mold and mildew is one reason off season storage matters, especially when protecting your boat for future adventures.


Protect Your Boat from Mold and Mildew at Simply Storage Idaho


Mold and mildew can cause significant damage to your boat, but by following these preventative steps, you can keep your vessel in top condition and ready for the next season. At Simply Storage Idaho, we offer secure and clean storage options to protect your boat from environmental damage.


Contact us today to learn more about our boat storage solutions and to reserve your spot.

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