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

cleaning moss on patio
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Oh, yuck. What's that gross-looking greenish black stuff on the 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, there is a need to find a sure way to remove it that won't destroy nearby landscaping and harm the environment with a blast of harsh chemicals. This method uses natural, super-versatile ingredients in most homes, like vinegar and Borax. While scrubbing harder on a patio or wall than, say, a kitchen sink is guaranteed, these cleaners should be able to tackle most cases of mold or mildew. Applications may need to be repeated for especially moldy areas. Remember, it will be worth the effort when guests come over and there will be no embarrassment of the unsightly mold.

What You'll 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

How to Formulate Mildew Remover

Dissolve in warm water together:

  • 1/2 cup of vinegar
  • 1/2 cup of Borax

Apply with sponge or spray bottle.

Difficulty: Easy

Time Required: One-half to one hour

Here's What You Do:

  1. Use a power nozzle with a strong spray to hose off the area that needs to be 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 bathroom, get a cup of coffee or water, 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 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 it starts to run out.
  6. Having some big fun now? Keep going until some progress is accomplished. Make sure to tackle the entire green-infested patio, walkway, or surface. Just think how strong that scrubbing arm will be. Switch arms for an evenly toned workout.
  7. Using a strong spray, again hose off the patio or surface 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. For those who don't trim the branches, hedges, and vines that are blocking out the sunlight, this chore will have to be done yet again—very soon.

If That Doesn't Work

For those who followed the instructions, scrubbed hard, and used the solution a few times without much luck, know that sometimes tougher measures are called for. 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 have 9.9 percent of alkyl dimethyl benzyl ammonium chloride. To give an idea of the chemicals that we're being dealing with, other household products that have the same ingredients include Lever 2000 Antibacterial Moisturizing Wipes and Nair Hair-Remover Kit.

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

Try revisiting the area in a week or two to keep on top of the mold and mildew. Persistence will pay off.