How To Remove Mildew From Canvas Boat Cover

How To Remove Mildew From Canvas Boat Cover
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Do you have a nice canvas boat cover that is now covered in mildew? Yeah, it’s an issue, one that needs to be dealt with. Right now, we’re here to figure out how to remove mildew from canvas boat covers.

What Is Mildew?

Mildew is actually a growth, a type of fungus which can infest more or less anything given the right conditions. Keep in mind that mildew is not the same thing as mold, although both are types of fungi, and both often caused by moisture. You can tell the difference because mold can be green, brown, blue, black, and other colors too, whereas mildew is white in color.

It looks like a soft and furry substance, and yes, it can smell pretty bad, almost like old winter coats being taken out of storage, somewhere they were damp for the duration of storage. Before we get any deeper into this topic, yes, mildew can be harmful to your health, both in people with and without allergies. It can cause runny noses, headaches, nausea, and with prolonged exposure also come more serious breathing concerns and other health issues too.

Why Does Mildew & Mold Occur?

Both mildew and mold often occur due to moisture. Yes, the fungal spores do have to be present, but to be fair, they are present in many different places, both in nature and manmade settings. Mold and mildew both grow abundantly when there is lots of moisture around, and the temperatures are right.

When it comes to your boat and the canvas cover you are using, mildew can occur on the boat if the canvas cover lets moisture in. Moreover, when it comes to the canvas cover itself, canvas is not totally waterproof, and it’s a type of fabric that will retain some moisture. Even with great waterproofing products, canvas boat covers are still fairly susceptible to mildew growth, especially when it comes to long term storage. As soon as there is moisture, the right temperature, mildew spores in the air, and a surface to cling to, such as your boat or the canvas cover, mildew is likely to grow.

Removing Mildew From A Canvas Boat Cover

What you need to know here is that mildew is not just a fungal growth per se, and besides obvious health concerns, it can be quite damaging too. In terms of fabrics, mildew can actually eat through and degrade them, and yes, this goes for canvas boat covers too. Mildew can actually eat holes straight through a canvas boat cover if left untreated for a prolonged period of time. So, let’s go over some techniques and tips on how to remove mildew from your canvas boat cover.

  • First things first, if you have mildew on your canvas boat cover, you need to scrub it off. Start by using a brush, or just your hands with a glove, to manually remove as much of the mildew as possible.
  • Next, you want to make a mild cleaning solution out of soap and warm water. Be sure to use a gentle soap, not some harsh detergent, as this may damage the canvas cover.
  • Hose off the cover with a good deal of pressure, and afterwards, use the water and soap combo, as well as a soft bristle brush, to scrub off as much of the mildew as possible. Yeah, this may take a while as mildew can be quite stubborn.
  • Now, if there are tough mildew spots that you cannot get off using a hose and brush, you will need to get yourself some fungicide. On the one hand, you can mix some water with bleach, which should be more than enough to kill mildew spores. Although, in some cases, bleach has been known to cause damage to canvas covers. If you are worried about this, you can use a professional grade fungicide designed specifically for canvas boat covers. This should do the trick.
  • Finally, now that you have managed to remove the mildew, you need to take steps to ensure that it does not occur again. One of the best ways to do this is to store your boat in a dry place, or in other words, not outdoors. However, if you do store your boat outdoors, or even inside for that manner, you want to wax the canvas cover, or spray it with a waterproofing agent. This will ensure that no moisture builds up on it, therefore preventing mildew from occurring in the first place.


Yes, mildew can be quite the issue when it comes to canvas boat covers, but thankfully, if you have the right tools at your disposal, it’s not all that hard to remove and prevent.

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