For asphalt or composite shingles, first check the shingle maker’s current care and warranty instructions; there is no single moss-removal method that is right for every roof. Oregon State University Extension recommends careful brushing, while the Asphalt Roofing Manufacturers Association (ARMA) recommends a specific bleach-and-water treatment for asphalt roofing. Both warn against pressure washing. If the roof is steep, high, slippery, or the instructions are unclear, hire a qualified roofing professional.
Start with the shingle manufacturer’s instructions
Identify the roofing material, then consult its manufacturer’s current cleaning and warranty guidance. ARMA says to ask the shingle manufacturer about moss and removal recommendations, and not to use other cleaning chemicals or methods without its approval. Do not assume advice for asphalt shingles also applies to metal, wood, or another roofing material.
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That check matters because credible guidance differs on physical removal versus chemical treatment. Oregon State University Extension recommends a brush or broom for asphalt or composite shingles; ARMA recommends a defined bleach treatment for asphalt roofing. Follow the method approved for your shingles rather than combining the approaches or adding an unapproved product.
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ARMA warns: “Never use a pressure washer to clean an asphalt shingle roof as this will cause granule loss and very likely premature failure of the roof system.” High-pressure water can strip the protective mineral granules. A pressure washer is not a shortcut for moss removal on asphalt shingles.
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- Kills moss quickly - see results in hours
- Non-staining formula can be used on roofs, walks, decks and patios
- Does not stain concrete, pavement, stucco, or wood
- Attaches right to your garden hose – no mixing
Choose a removal method only if the manufacturer allows it
Careful brushing: Oregon State Extension’s approach
Oregon State University Extension recommends using a brush or broom to remove moss from asphalt or composite shingles. Use it gently: the aim is to dislodge moss, not scrape the shingle surface. Forceful brushing or scraping can remove granules, so stop if the surface is being abraded and defer to the manufacturer’s directions.
Bleach treatment: ARMA’s asphalt-roofing guidance
For asphalt roofing, ARMA recommends mixing laundry-strength liquid chlorine bleach and water in a 50:50 ratio, spraying the solution on the affected area, leaving it for 15 to 20 minutes, then rinsing thoroughly with low-pressure water. ARMA says not to let the mixture dry completely, to protect landscaping, and to use appropriate personal protective equipment. Moss may loosen over time, so do not try to force it off with a pressure washer.
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- Exclusive micro-granule formula
- Kills moss quickly
- Use on roofs, patios, sidewalks, brick and unpainted cement
- Non-staining, non-corrosive to galvanized gutters
This is ARMA’s recommendation for asphalt roofing, not a universal recipe. Do not transfer it to another roof material, bleach formulation, or concentration, or use it if the shingle manufacturer does not approve it. Follow the product label and take care to keep runoff off plants and other vulnerable surfaces.
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- Potassium salts of fatty acids: Oregon State University Extension describes these soap-based products as breaking down moss cell membranes. Extension characterizes them as noncorrosive, with minimal risk to people and animals; still avoid overspray on plants, rinse any plants accidentally treated, and rinse tools. Check both the product label and roof-maker guidance for compatibility.
- Zinc sulfate: Oregon State Extension discusses it as a roof-moss treatment, but warns that zinc sulfate corrodes copper. Do not use it where copper gutters, downspouts, or flashing could be exposed. Follow the treatment label and the roof manufacturer’s instructions.
- Zinc or copper strips: ARMA does not recommend adding these to an existing asphalt roof. Installation can require exposed nails that may leak or disturb the shingle sealant bond, creating a wind-damage risk.
Extension’s broader roof-moss guidance includes zinc sulfate quantities for particular areas and conditions, including wood-roof discussion. Those quantities should not be transferred to asphalt or composite shingles or substituted for a product label.
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- Moss and algae killer and cleaner: kills moss, algae, lichen, mold, and mildew wherever it grows
- Protection for months: kills within hours and protects for months
- 2-In-1 killer and cleaner: use on lawns, patios, roofs, buildings, decks, driveways, mulch, and more
- Kills within hours: moss will quickly turn yellow and then brown, but must be physically removed once dead
Reduce the conditions that let moss return
Moss can attach to asphalt and metal roofs, lift shingles, and allow water to reach underlying layers, according to Oregon State University Extension. To reduce favorable growing conditions:
- Trim overhanging branches to improve sunlight and airflow.
- Clear roof debris rather than letting it collect in shaded areas.
- Keep drainage working so water does not linger.
Extension describes moss control as temporary: commercial treatments may slow new growth but can require reapplication. Use only a treatment approved for the roofing material and follow its label.
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- New & Improved Nozzle! Xtreme Reach Hose End Outdoor Cleaner attaches to garden hose; jet tip sprays up to 30ft to remove green and black stains caused by moss, mold, mildew, and algae on roofs and siding; fan tip provides quick application to driveways and decks; no rinsing
- Spray dry surface on a cool day to avoid rapid evaporation of product, do not rinse, apply when rain is not forecasted within 4-5 hours, apply when the temperature is above 55° F
- Cleans over time with the wind and rain, green stains clean up within 1-2 weeks, black stains or heavy, stubborn stains can take several months, long-established stains may take 6-12 months; surfaces can stay clean up to 1 year or longer
- It is bleach free and non-acidic; spray 100 feet away from lakes, ponds, rivers, and streams and flush plants with water before and after application
- Each bottle treats up to 2,000 square feet, heavy stained and porous surfaces will absorb more product
Decide whether it is safe to work on the roof
Roof moss removal is not suitable for everyone. Oregon State University Extension advises wearing shoes with strong traction; placing a ladder on stable ground, securing it where possible, and extending it at least three feet above the roofline; and moving tools with a bucket and rope rather than carrying them up a ladder. Extension recommends fall-protection belts and lines on steep roofs, near edges, or where eaves exceed 16 feet.
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If the roof is steep, high, slippery, or otherwise unsafe—or you cannot use the maker-approved method confidently—stay off it and hire a qualified local roofing professional. Ask what method they will use and whether it is approved for your roof material.
Quick Recap
Best Value
- Wet & Forget Concentrate Outdoor Cleaner removes green and black stains caused by moss, mold, mildew, and algae, no scrubbing, no rinsing, no pressure washing, just wet it and forget
- Surfaces including driveway, patio, roof, siding, deck, vinyl, wood, concrete, canvas, aluminum, and upholstery
- Mix 1 part Wet & Forget with 5 parts water in a garden sprayer, spray dry surface on a cool day to avoid rapid evaporation of product, do not rinse, apply when rain is not forecasted within 4-5 hours
- Apply when the temperature is above 32° F; unused product can be stored mixed and ready in sprayer for future applications
- Cleans with the wind and rain, green stains clean up within 1-2 weeks, black stains or heavy, stubborn stains can take several months, long-established stains may take 6-12 months; surfaces can stay clean up to 1 year or longer
Guidance cited
- Oregon State University Extension, “How to remove moss from my roof?”
- Asphalt Roofing Manufacturers Association, “Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems”
- Kym Pokorny, Oregon State University Extension, “How to control roof moss and prevent long-term damage”
- Ask Extension, “Environmentally Safe Moss Prevention for Asphalt Roofs,” expert answer dated June 17, 2026
- Asphalt Roofing Manufacturers Association, “Algae Discoloration of Roofs”
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