How to Clean Cedar Shingles

Co-authored by wikiHow Staff

Last Updated: October 25, 2022

Cedar shingles are a time-tested roofing method and are also visually appealing. They’re also prized for their durability, resistance to rot, and resistance to insects. Despite this, cedar shingles still need to be regularly cleaned to maintain their appearance and effectiveness. Ultimately, by taking steps to remove growth on your shingles, washing them, and doing some work to prevent deterioration in the future, you’ll be better able to keep your cedar shingles clean.

Things You Should Know

To gently clean your cedar shingles, try rinsing them with a low-pressure hose, or scrub them with a soft-bristled brush if they need a little more cleaning.
If you have stubborn moss or mildew growing on your shingles, try spraying your roof with a citric-based cleaner or a diluted bleach and detergent mixture.
Use a long-handled broom or pole to clear leaves, sticks, and debris from your roof to help prevent moss, mold, and lichen from growing on your shingles.
Brighten your roof by spraying it with a 5% solution of oxalic acid.

Part 1

Part 1 of 2:

Removing Moss, Mildew, and Lichen

1
Conduct a soft wash on your roof. A soft wash, also known as a non-pressure wash, is where you take low pressure water and spray down a surface. This is important, as standard high pressure power washes might damage cedar shingles.
- Use a 12-volt pump system with pressure of about 60 PSI.
2
Scrub the shingles with a bristle brush. Once you’ve soft washed your roof, you may still need to scrub it with a soft bristle brush. A bristle brush will help loosen moss, mildew, lichen, and other growth on the shingles.
- You can use a small brush to scrub shingles individually or a large brush on a pole to clean many at one time.
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3
Create a bleach mixture. Mix one part bleach and five parts water. Sprinkle in several tablespoons of powdered detergent. Stir the mixture and pour it into a spray bottle or something similar.
- Use proper safety equipment, including goggles and gloves.
- Do not use liquid detergent or a detergent that contains ammonia. This could cause a dangerous chemical reaction with the bleach.^{[1]
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4
Use a citric-based solution if you don’t want to use bleach. Citric-based solutions are non-toxic and quite effective If a tradition bleach solution did not work, you should spray citric solution on your roof. These solutions are available at major hardware stores or can be purchased online.
- Citric cleaning solutions should be specially formulated for cedar shingles and may include algaecide, mildewcide, and fungicide.
- Commercially available citric solutions may also contain a water-based oil that will help rehydrate your shingles.
5
Spray the mixture. Use a garden sprayer or similar device to spray the mixture on your cedar shingles. Make sure to get the entire surface of your cedar shingle roof. Pay special attention to areas where there might still be moss or lichen remnants.
- Allow the bleach or citric mixture to sit for about 15 minutes.^{[2]
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6
Rinse the surface. After soft washing and scrubbing the shingles, you should take a common garden hose and rinse the shingles down. This will help remove any bits and pieces of moss or lichen that remain after you’ve scrubbed the shingles.
- The water from your garden hose should have about a 40 PSI.
- Rinse your roof from the top down, so you can clear off all residual debris.

Part 2

Part 2 of 2:

Maintaining Your Roof

1
Trim overhanging tree limbs. One of the most important ways to maintain your roof is to remove any tree branches or limbs that overhang your roof. Not only will these limbs contribute to the accumulation of debris on your roof, but the shade they help create will encourage the growth of mold and lichen.
- You may be able to cut smaller limbs or branches by yourself.
- If you have large limbs that overhang your roof, you may need to call in a tree cutting service.^{[3]
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2
Remove leaves and other debris. You should periodically remove leaves, sticks, and other debris from your roof. Accumulated debris will increase the amount of moisture on your roof and encourage the growth of mold and lichen.
- If you have a long broom or pole, you may be able to remove a lot of debris from the ground or from a ladder.^{[4]
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3
Replace damaged or rotten shingles. Use a hammer to remove any nails or tacks that secure shingles to your roof or other shingles. Remove the damaged shingle. Then, tack and nail down a replacement shingle.
- If you’re not comfortable replacing a shingle yourself, you should contact a licensed roofer or contractor to do it for you.
4
Apply a 5% oxalic acid solution on your roof. This solution will help neutralize the blue-black stain that occurs on shingles overtime. In the end, you’ll have shingles that appear brighter.
- Be very careful using oxalic acid, as it is a toxic substance.
- Oxalic acid won’t keep shingles bright. If you don’t remove the source of the stain (usually iron from certain nails), you’ll have to apply it again.^{[5]
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5
Clean your roof regularly. How often you clean your cedar shingle roof depends on the climate you live in. To determine this, you need to consider the challenges the environment you live in pose to your roof.
- Cedar shingles in wet and overcast climates should be cleaned yearly.
- Cedar shingles in sunny and dry climates may only need to be cleaned every 2 to 3 years.^{[6]
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Warnings

Make sure to use a safety harness to secure yourself to the roof.

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Consider using roofing shoes in addition to a safety harness.

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Use safety glasses when working with bleach or other chemicals.

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