Mold and mildew are the bane of every boat owner. These fungi can do serious damage to a boat if not kept in check. And mold doesn’t create problems only for your boat. Mold can cause health issues, including joint pain, headaches, fatigue, and respiratory problems.

If that isn’t enough to motivate you to prevent mold and mildew in your boat, know that most insurance policies don’t cover mold or mildew damage. Once an infestation has done its work, you’ll be left with costly repairs and the stress of addressing them.

This article will share what to do if mold and mildew have already taken up residence in your boat, and will show you how to prevent these fungi from causing problems in the future. We’ll examine how to protect your investment while you’re out on the water as well as while your boat is covered, in storage for the season.

Mold and mildew will require you to be vigilant to keep them away, but dealing with either of these growths is fairly straightforward. Here’s what you need to know.

What’s the Difference Between Mold and Mildew?

When addressing mold and mildew issues, it’s helpful to know how they’re similar and how they differ. Mold and mildew are fungi that share many of the same characteristics: Both thrive in moist, dark areas, and they can grow on a wide variety of surfaces — from food, to shower stalls, to paper.

Mold is usually black or green and is a result of a large infestation of spores. It can appear either fuzzy or slimy. Mildew, on the other hand, most often looks like white or gray powder dusting the surface of an area.

Mold is tough to control once it starts. And surprisingly, mold doesn’t require warmth to survive. Mold can withstand cold climates, since freezing temperatures don’t kill spores. When the weather warms back up, the mold will take off growing again.

Mildew is easier to treat than mold, since it’s not as hardy. But it can cover wide swaths of surface area, and if it gets into fabrics or paper (such as books), you’re better off just tossing those items.

What to Do If You Already Have Mold or Mildew

If you’ve already experienced a mold or mildew problem, your first priority is to get rid of it. These fungi can cause permanent damage to a boat if left alone for even a short period of time. Although it seems like there’s an endless list of tasks to address on a boat, this one should be moved to the top.

Mold and mildew removal can be hazardous to your health, so you’ll want to follow proper procedure when you’re around it. You’ll also need to know effective solutions to combat it. We recommend an 8-step process.

  1. Protect Yourself — Before you begin, you should put on a respiratory mask (the EPA recommends an N95 mask, to prevent inhalation of spores), rubber gloves, and protective eyewear (to keep mold from getting into your eyes and ears as well).
  2. Do an Initial Scrub-Down — Remove as much of the mold and mildew as you can with a simple soap and water solution. It’s helpful to use a scrub brush.
  3. Try All-Natural — If your infestation isn’t severe, you may be able to get away with an all-natural cleanser like tea tree essential oil. Tea tree oil is a natural fungicide. If it does the job, you won’t have to deal with harsh odors from heavier-duty substances. To use, put about ten drops of tea tree oil into a cup of water, inside a spray bottle. Shake it up and then spray wherever you find mold and/or mildew. Allow it to sit for several minutes, then use a brush to remove the fungi. Vinegar is another all-natural cleaner that is often effective against mildew and mold.
  4. Bring In the More Powerful Solutions — If tea tree oil and vinegar aren’t strong enough for your mold or mildew problem, you’ll need a heavier-duty solution. We recommend diluted bleach (one part bleach, three parts water) or 3% hydrogen peroxide. While these substances are highly effective against mold, they will both bleach surfaces and shouldn’t be used on wood. Be sure to test them on an inconspicuous area first.
  5. Or Use a Cleaner Specifically Made for Mold — There are cleaners made specifically for mold, and some are designed to be safe for upholstery. These cleaners also have the benefit of a softer odor than bleach.
  6. Fumigate — To make sure you get rid of all the spores, you can follow up with a chlorine dioxide penetrating vapor that will not only kill the mold, but will also eliminate odor.
  7. Apply a Mildew Blocker — If your mildew problem is especially insidious, you may consider applying a mildew blocker. These products work only temporarily, but they do help in the short term.
  8. For Sails — If your boat has sails, you’ll want to take special precautions with them. Always fresh-water rinse sails and allow them to fully dry before stowing them. If you do experience a mildew infestation on a sail, keep it away from the clean ones to avoid having the fungus spread. Cleaning up mold or mildew on sails requires specialized care, depending on what your sails are made of. Kevlar sails should be cleaned only with water. Nylon or Dacron sails can be cleaned with a lemon juice and water solution; if that doesn’t work, then try Lysol.  

How to Prevent Mold and Mildew in the First Place

It’s much better to prevent mold and mildew in your boat than to wait until you have an infestation and then be forced deal with it. The key to preventing these fungi is to eliminate the conditions they need in order to grow. Here’s what you’ll need to do.

  • Immediately Fix Leaks  — Fixing leaks is not something you can put off if you want to avoid mold and mildew. Leaks create a prime growing environment for mold. Anytime you notice pooling water, make it a priority to find the source and fix it.
  • Keep the Boat Clean — Mold and mildew enjoy dirt and grime, so it’s smart to clean up any crumbs, spills, and water that make their way onto your boat. It’s helpful to create a cleaning schedule that you can easily glance at to make sure you’re keeping up with all cleaning tasks.
  • Allow Air to Flow — Stagnant air is attractive to mold and and mildew, because it allows condensation to form. If air is flowing throughout your boat, fungi won’t be able to thrive. Make sure your boat is well-ventilated, and run fans to encourage the air to move. Boat cover vents are also helpful. During the times when the boat is closed up, many boat owners use dehumidifiers to ensure airflow and allow the boat to dry.
  • Spot Check — The key to solving a mold or mildew problem easily is to catch it early. Spot checking out-of-the-way nooks and crannies will prevent an issue from becoming worse. Pay special attention to:
    • Hatches
    • Chain plates
    • Deck core
    • Stanchions
    • Cockpit scuppers
    • Deck-stepped masts
    • Closets
    • Cabinets
    • Drawers
    • Hatch roller blinds
    • Curtains
  • Use DampRidDampRid will remove dampness from the air, making your boat less attractive to mold and mildew. This product contains a non-toxic, inorganic mineral salt called calcium chloride that naturally absorbs moisture. DampRid comes in individual containers that you can pop open and place in various locations throughout your boat. And the containers are refillable.

If You’re Storing Your Boat for the Season

If you’re storing your boat over a period of time, you’ll want to prepare it in a way that’s designed to prevent mold and mildew problems. Thorough preparation now will keep you from experiencing expensive damage next season. Here are the essentials.

  • Use a Vented Cover — Install a vented boat cover, which will encourage airflow throughout your boat.
  • Remove All Items That Could Attract Moisture — Mattresses and bedding, life jackets, seat cushions, clothing, food, books, and other items should be taken out of the boat. Remove everything that doesn’t have to stay in the boat.
  • Open Closets, Drawers, and Cabinets — In order to allow airflow, crack open closets, drawers, and cabinets.
  • Use a Dehumidifier — Many boat owners swear by dehumidifiers. Although they don’t work well while people are coming in and out of the boat, because they can’t keep up with the moist air being let in, they are a good preventative for boats that are in storage.
  • Lift a Few Floorboards — If you lift a few floorboards, you’ll ensure the bilge is getting fresh air as well.

Mold and mildew infestation can be a concerning threat, but if you take precautions to prevent these fungi, and if you address any growth issues immediately, your boat should be safe. Diligence is key to being able to enjoy your boat worry-free!

Next Article: The Ultimate Checklist to Get Your Boat Ready for Spring