How to Remove Moss, Mold, and Mildew From Patios and Outdoor Surfaces

Cleaning Your Yard and Outdoor Space

cleaning moss on patio
Use care when pressure-washing brick or stone surfaces. Diane Macdonald/Getty Images

Oh, yuck. What's that gross-looking greenish black stuff on your concrete patio? Probably mold, mildew, or moss—the dreaded three M's. Damp or moist conditions from rain or humidity can encourage mold and mildew to grow in those nooks and cracks of concrete pavers or bricks.

Whatever it is, you need a sure way to remove it that won't destroy nearby landscaping and harm the environment with a blast of harsh chemicals. The method we suggest uses natural, super-versatile ingredients you probably have at home, like vinegar and Borax. While you may need to scrub harder on a patio or wall than, say, a kitchen sink, these cleaners should be able to tackle most cases of mold or mildew. Applications may need to be repeated for especially moldy areas. Just think: It will be worth the effort when you want to enjoy your yard and entertain guests without the embarrassment of unsightly mildew.

What You Need

  • Bucket
  • A large bottle of white vinegar
  • Water
  • Hard-bristle scrub brush (non-metallic)
  • Knee pads
  • Hose with power nozzle or a power washer (pressure washer)
  • A strong arm (or two)
  • Perseverance

Mildew Remover

  • Dissolve together: ½ cup of vinegar
  • ½ cup of Borax in warm water
  • Apply with sponge or spray bottle

Difficulty: Easy

Time Required: One-half to one hour

Here's How:

  1. Use a power nozzle with a strong spray to hose off the area you want to clean.
  2. Mix ingredients in the bucket.
  3. Apply the solution with a sponge. Do one area at a time.
  4. Allow cleaning ingredients to permeate surface(s) for a few minutes. Go to the loo, get a cup of coffee or whatever, and return. If the mildew or moss is especially aggressive, allow the solution to soak in for a longer amount of time, like a half hour or more.
  5. Don a pair of waterproof rubber gloves, get down on your hands and knees (here's where knee pads might come in handy), grab the hard-bristle brush and start scrubbing. Scrub in circular, clockwise or counterclockwise motions, tackling about a 3-foot x 3-foot area at a time.Dip the brush into the solution if you start to run out
  6. Having some big fun now? Keep going until you see some progress. Make sure you tackle the entire green-infested patio, walkway, or surface. Just think how strong your scrubbing arm will be. Switch arms for an evenly toned workout.
  7. Using a strong spray, again hose off the patio or surface you just scrubbed. If you followed directions, used the right amount of pressure while scrubbing, and didn't slack off, the green patio should start to look concrete-colored again. Or, at least less green. Choose a time of day when there is as much sunlight as possible to dry the rinsed-off patio. Moss and mildew love dampness and shade.
  1. f you don't trim those branches, hedges, and vines that are blocking out the sunlight, you'll find yourself having to do this chore yet again—very soon—on a day when you could be relaxing or at least doing some other kind of DIY project.

If That Doesn't Work

You followed the instructions, scrubbed hard, and used the solution a few times—without much luck. Sometimes you have to get tougher. A product like Wet & Forget should do the job. While the label says it is bleach-free, phosphate-free, non-acidic, and safe near plants and on all outdoor surfaces (when used as directed), its ingredients are alkyl dimethyl benzyl ammonium chloride 9.9 percent. To give you an idea of the chemicals you're dealing with, other household products that have the same ingredients include Lever 2000 Anti-bacterial Moisturizing Wipes and Nair Hair-Remover Kit.

Follow the directions on the container of your cleaning product, making sure that the previous cleaning solvents have been thoroughly rinsed off with a strong blast from the hose. While the product you use may claim that scrubbing isn't necessary, you will probably have to keep those sleeves rolled up and continue to scrub the moldy/mossy area until it is free of the green stuff.

You may need to revisit the area in a week or two to keep on top of the mold and mildew. Persistance will pay off.