How to Remove Mildew and Algae from a Wooden Fence

Co-authored by Andres Matheu

Last Updated: March 22, 2023 Approved

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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Remove any other obstructions.

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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.
If stains remain proceed to the next step.
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Scrub the stained areas on the fence if some stains remain after power washing. ^{[2]
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- 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.
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Method 2

Method 2 of 2:

Hand Scrubbing to Remove Mildew and Algae from Wood Fences

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You could do this with a garden hose.
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Question

Should I use a bleach solution or buy an algae remover?

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.

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Question

Could I use a bleach solution to clean a stained cedar fence?

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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.

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Question

Is there any spray I can use on a wooden fence to treat it for algae?

June Higgins

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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.

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Trimming plants away from the fence to expose it to more sun and air may naturally “heal” the fence.

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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.

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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.

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Don’t let the pressurized water stream hit plants; even the trunks of large trees could be damaged.

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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

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How to Remove Mildew and Algae from a Wooden Fence

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

Hand Scrubbing to Remove Mildew and Algae from Wood Fences

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