How to Remove Mildew and Algae from a Wooden Fence

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Over time, wooden fences can get covered in algae and mildew. The growth generally occurs in shaded, moist locations. There are several ways you can clean the algae and mildew off a fence so that it looks better.

Method 1
Method 1 of 2:

Using a Power Washer to Remove Mildew and Algae from Wood Fencing

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  1. How.com.vn English: Step 1 Trim and tie back plants.
  2. How.com.vn English: Step 2 Cover tender plants with a tarp or invert buckets over them.
    Remove any other obstructions.
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  3. How.com.vn English: Step 3 Set the power washer on a lower pressure setting such as 1500 to 2000 psi.
    [1]
  4. How.com.vn English: Step 4 Stand about 2 feet (0.6 m) away from the fence and hose it down.
    You can move closer in for heavily stained spots but don’t keep high pressure on any spot for too long. Move the sprayer in a slow, sweeping pattern.
  5. How.com.vn English: Step 5 Let the fence dry if the mildew and algae disappear from the fence.
    If stains remain proceed to the next step.
  6. How.com.vn English: Step 6 Scrub the stained areas on the fence if some stains remain after power washing.
    [2]
    • Pour a solution of one part household bleach to two parts water into a bucket. There is no need to stir.
    • Use a scrub brush to clean the remaining stains with the solution. Be careful not to get bleach solution on your plants.
    • Repeat the power washing on the stained areas you scrubbed.
  7. How.com.vn English: Step 7 Check the fence and sand any rough areas.
  8. How.com.vn English: Step 8 Sink any protruding nails or screws and repair any damaged wood.
  9. How.com.vn English: Step 9 Apply wood preservative, stain or paint to the fence after it dries prevent future algae and mildew growth.
    [3]
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Method 2
Method 2 of 2:

Hand Scrubbing to Remove Mildew and Algae from Wood Fences

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  1. How.com.vn English: Step 1 Cover plants with tarps or inverted buckets.
  2. How.com.vn English: Step 2 Mix a solution of one part household bleach to two parts warm water in a bucket.
  3. How.com.vn English: Step 3 Add a teaspoon of a mild soap that is safe to mix with chlorine bleach  to each gallon or liter of water in your bucket.
  4. How.com.vn English: Step 4 Scrub the stained areas of the fence with a scrub brush, being careful not to get the solution on plants.
    [4]
  5. How.com.vn English: Step 5 Rinse the fence with clean water.
    You could do this with a garden hose.
  6. How.com.vn English: Step 6 Let the fence dry.
  7. How.com.vn English: Step 7 Repair any damaged areas, sink protruding screws or nails, and sand rough areas.
    [5]
  8. How.com.vn English: Step 8 Consider painting the fence with a paint that has an algae and mildew preventative in its formula.
    [6]
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Community Q&A

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  • Question
    Should I use a bleach solution or buy an algae remover?
    How.com.vn English: Community Answer
    Community Answer
    It depends. Too strong a solution or too hard a brush could streak the paint and wood. You could try using a pressure washer.
  • Question
    Could I use a bleach solution to clean a stained cedar fence?
    How.com.vn English: Community Answer
    Community Answer
    Yes, provided it is a mild solution of, say, one part bleach to five parts water. Mold and Algae will absorb the bleach with the water and should die off within three to five days. Eye and skin protection are essential, and wash your hands and any other points of skin contact immediately afterward.
  • Question
    Is there any spray I can use on a wooden fence to treat it for algae?
    How.com.vn English: June Higgins
    June Higgins
    Community Answer
    Spraying ‘Elbow Grease’ is quite effective for removing green algae from a wooden fence.
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      Tips

      • Test a small, inconspicuous area of your fences first to see if the power washer leaves ridges or damages the fence.
      • Trimming plants away from the fence to expose it to more sun and air may naturally “heal” the fence.
      • Sometimes a garden hose with a “power wash” nozzle will have enough power to clean mildew and algae off a wood fence.
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      Warnings

      • Don’t set the pressure on a pressure washer too high or it will damage the fence.
      • Very old, rotting fences cannot be power washed without ruining the fence. You may have to replace older sections of fence that are badly mildewed or algae covered.
      • Don’t let the pressurized water stream hit plants; even the trunks of large trees could be damaged.
      • Keep children and pets away from the fence while you power wash it.
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      Things you’ll need

      • Power washer
      • Scrub brush
      • Buckets or tarps to cover plants
      • Household bleach
      • Mild soap that’s safe to use with bleach
      • Tools to repair fence if needed, hammer, screwdriver, etc.
      • Sandpaper
      • Paint, stain or wood preservative

      About This Article

      How.com.vn English: Andres Matheu
      Co-authored by:
      Commercial Painter
      This article was co-authored by Andres Matheu. Andres Matheu is the Owner of Hömm Certified Painting Systems, an Interior and Exterior Residential painting business based in the Washington, DC Metro area. Andres specializes in interior and exterior residential painting, color consultations, cabinet refinishing, wallpaper removal, and epoxy flooring among other services. An EPA Lead-safe Certified Firm, Hömm Certified Painting Systems has been awarded the Best of Houzz 2019 Service, Angie's List Super Service Award 2019, and Northern Virginia Magazine's 2018 Best Home Experts (painters) award. This article has been viewed 366,502 times.
      2 votes - 50%
      Co-authors: 18
      Updated: March 22, 2023
      Views: 366,502
      Categories: Fences and Gates
      Article SummaryX

      If you want to remove mildew and algae from a wooden fence using bleach, start by covering the plants with tarps or inverted buckets so they aren’t harmed by the solution. Then, mix 1 part bleach with 2 parts warm water. Next, add 1 teaspoon of mild soap per gallon of water, if it is safe to mix with bleach. Scrub that solution onto the stained areas of the fence and rinse it off with a hose. Keep reading to learn how to prevent future algae or mildew growth!

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      Thanks to all authors for creating a page that has been read 366,502 times.

      Reader Success Stories

      • How.com.vn English: Liz Douglas

        Liz Douglas

        Sep 18, 2016

        "The bleach and water and mild soap mix for scrubbing the fencing helped. I had been using a wire brush and it..." more
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