How to Clean Mildew, Mold, and Moss from Canvas Awnings

Canvas awnings on your home or RV are usually durable to the elements, but even they could develop some unsightly mold and mildew over time. We know that you want to make your awnings look like the day you first put them up, and the good news is that they're really easy to clean with some supplies you probably already have at home. Keep reading for the best way to get that pesky mildew off your awnings and how to stop it from coming back.

Part 1

Part 1 of 3:

Removing Dirt and Debris

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1
Set up a ladder to clean off your awnings. Awnings are easiest to clean when you leave them open or up in their frame. Choose a ladder that has a step or platform on top where you can easily keep your cleaning supplies. Place a ladder next to your awning so you can climb up safely and reach the canvas.^{[1]XResearch source}
- If you’re cleaning an RV awning, you may only need a step ladder instead.
Cover the ground and nearby items with plastic tarps. The cleaning solution to remove mold contains bleach, which could damage plants and any other objects directly under the awning. Put a plastic tarp on the ground underneath the awning to catch any spills or drips while you’re cleaning.^{[2]XResearch source}
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3
Brush debris off the awning with a soft-bristled broom. Start at the top of your awning and brush down the surface with your broom. Apply gentle pressure to knock off any leaves, sticks, twigs, cobwebs, or dirt that accumulated on the awning. Once you clear the awning of debris, it’ll be a lot easier to fully clean.^{[3]XResearch source}
- Leaving debris on your awning can cause damage and make it more likely for mosses and mildew to form.
- Mildew looks like gray or black powder that sticks on your awning even after you brush it.^{[4]XResearch source}
- Green or brown splotches on your awning are either moss or lichens. You can still get rid of both the same way you’d remove mildew.

Part 2

Part 2 of 3:

Cleaning Mold and Mildew off a Canvas Awning

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1
Hose down the awning. Spray your awning with a garden hose to get it completely wet. If you don’t have a hose, just climb your ladder and wipe your awning with a wet cleaning cloth or sponge.^{[5]XResearch source}
- The water will make it easier for you to spread the cleaning solution so the mildew comes off quicker.
2
Mix a cleaning solution with bleach and water in a bucket. Add ¹⁄₂ c (120 ml) of chlorine bleach, , and 1 gallon (3.8 L) of water in a large bucket and stir until it’s thoroughly combined. The bleach will kill any mold spores on your awning.^{[6]XExpert SourceMike Kapur
Certified Mold Assessor & Home Inspector, Sonic Home InspectionsExpert Interview. 19 August 2020.}
- Since bleach can irritate your skin, put on a pair of rubber gloves before you start cleaning.
- For a natural alternative, use white vinegar.^{[7]XExpert SourceMike Kapur
  Certified Mold Assessor & Home Inspector, Sonic Home InspectionsExpert Interview. 19 August 2020.}
- You can instead use a commercial mold and mildew remover if you don’t want to mix your own.
- Test your cleaning solution on an inconspicuous spot of your awning to make sure it doesn’t make the colors bleed. Let the solution sit for 20 minutes before rinsing and checking for discoloration.
- Never mix bleach or other cleaning solutions with soap, as it can create toxic gas.^{[8]XResearch source}
3
Wipe the cleaning solution onto your awning with a cloth or sponge. Dip the clean cloth or sponge into your cleaning solution and spread it onto your awning. Rewet your cleaning cloth as it dries out until you soak the awning completely.^{[9]XResearch source}
- Your ladder could be slippery if you spill any of your cleaning solution on it, so keep both feet planted so you don’t lose your balance.
- If you aren’t able to reach parts of your awning, use a long-handled sponge mop instead.^{[10]XResearch source}
4
Let the cleaning solution sit for 15 minutes. Your cleaning solution needs time to soak into the fabric so it can kill the mold and mildew. Leave your awning open the whole time while the solution soaks in.^{[11]XResearch source}
- Avoid letting the cleaner sit for 20 minutes or longer, since it may discolor your awning.
5
Scrub the canvas with your broom. After the cleaning solution has had some time to soak in, take your soft-bristled brush and scrub the top side of the awning. Apply gentle pressure to break apart the moss, mildew, and mold on the surface.^{[12]XResearch source}
- If the cleaning solution starts to dry anywhere, re-soak the area before you scrub.
- Avoid using brushes with stiff bristles since they could damage the finish or fabric.
6
Rinse the awning with water. Once you scrub the whole awning, spray it with clean water from your hose or wipe it down with a damp cloth. Continue rinsing your awning until the water runs clear to ensure there isn’t any cleaning residue left on the fabric.^{[13]XResearch source}
- Cleaner residue left on your awning could cause fabric discoloration when it’s left out in the sun.
7
Let the awning air-dry completely. If you left your awning attached to its frame, just keep it open so it can dry out. After a couple of hours, the sun and breeze will dry your awning out so it’s safe to put away.^{[14]XResearch source}
- Rolling up or putting your awning away while it’s still wet makes it easier for mold or moss to grow back.
- If there's any mildew left on the awning, soak it in your cleaning solution and gently scrub it again. It may take a few cleanings to completely remove stubborn mildew or mold.
8
Apply a reproofing spray onto your awning. Using a cleaning solution may have removed the water- and stain-proofing surface from your awning. Get a reproofing spray and apply an even coat directly onto the canvas once it’s dry. After you apply the first coat, let it dry for 5–10 minutes. Apply a total of 3 coats of the reproofing spray to keep your canvas awning protected.^{[15]XResearch source}
- If you forget to reproof your awning, mold and mildew will grow faster since there isn’t a waterproof barrier over the fabric.

Part 3

Part 3 of 3:

Preventing Mold and Mildew

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1
Hose down the awning monthly. Stand on the ground or on a ladder, and use a low-pressure attachment on your hose to spray the canvas until it’s thoroughly soaked. After you rinse it, leave it open until it’s completely dry.^{[16]XResearch source}
- Hosing down the awning removes dirt, organic matter, and other things that could lead to mildew growth.
2
Clean your awnings yearly. Carve out a day each year to clean your awnings so they never have a chance to get too dirty. Just soak the awning with water, scrub on a mixture of 1 gallon (3.8 L) of water and ¹⁄₄ cup (59 ml) of mild liquid soap, rinse it out completely, and let it dry. That way, you remove any pollutants, organic matter, dirt, and contaminants from the surface.^{[17]XResearch source}
- You only need to use bleach if you notice mildew or mold growing on your canvas.
Moisture is what causes mold and mildew to grow.^{[18]XExpert SourceMike Kapur
Certified Mold Assessor & Home Inspector, Sonic Home InspectionsExpert Interview. 19 August 2020.} Whenever you need to roll up an RV awning, wait until it’s completely dry before storing it. If you’re taking your awnings down for the season, make sure you keep the awning in a well-ventilated area that’s safe from moisture, or else mildew or mold can grow on the fabric.^{[19]XResearch source}

Expert Q&A

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Question
Is there an easier cleaning solution that doesn't involve bleach?
Dario Ragnolo
House Cleaning Professional
Dario Ragnolo is the Owner and Founder of Tidy Town Cleaning, a home cleaning service in Los Angeles, California. His business specializes in residential & commercial cleaning. He is a second generation home cleaning expert, who grew up around his parents cleaning business in Italy.
Dario Ragnolo
House Cleaning Professional
Expert Answer
Yes, you could always just use laundry detergent and hot water. Apply it with a brush and then rinse the canvas off.
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Will a weak chlorine solution, used to clean a canvas awning, discolor the painted deck under the awning?
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This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
How.com.vn Staff Editor
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The solution may discolor your deck, so put down a layer of plastic tarps to catch any drips.
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Will this solution discolor a dark green canvas?
Community Answer
No, it will not, as long as the canvas is designated "outdoor" or "indoor/outdoor." You can clean most outdoor furniture and cushions without any problems. I own a pressure washing company and I've washed several outdoor surfaces and the main chemical I use is pool chlorine (bleach). I never mix it stronger than 5 parts water/detergent to 1 part chlorine.
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Warnings

Avoid mixing bleach with any other cleaners, including vinegar or soap, since it can create harmful gasses.^{[20]XResearch source}
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