The safest roof moss removal on asphalt shingles is to loosen the moss with a moss-specific cleaner, rinse at low pressure and lift off what comes free by hand. Never use a pressure washer, brush or broom: they strip the granules that protect the shingle. If the moss is thick or the roof is steep, call a roofer first.
Method table
Roof moss removal methods compared
Method
What the sources say
Watch out for
Moss-specific cleaner, bleach-free
IKO’s first suggestion: an EPA-rated moss cleaner, sprayed on, left for the time on the label, then rinsed at low pressure.
Rinse every trace off. Leftover cleaner can damage shingles.
Zinc sulfate
OSU Extension: 3 pounds of powder in 9 gallons of water covers 600 to 1,000 square feet. Applied with a pump sprayer after cleaning the roof.
Do not use it if you have copper gutters, downspouts or flashing. Zinc corrodes copper.
Potassium salts of fatty acids
OSU Extension: soap-based, biodegradable and noncorrosive. It kills moss by damaging cell membranes.
Keep spray off surrounding plants.
Diluted bleach or dish soap mix
IKO: two cups of bleach in two gallons of water, or eight ounces of dish soap in two gallons. Leave 15 to 20 minutes, then rinse gently.
Strong bleach can permanently damage shingles. Wet roofs are slippery.
Pressure washer, brush or broom
ARMA and IKO: do not use them on asphalt shingles.
Strips granules, breaks the adhesive and can cause leaks.
Metal strip along the ridge
IKO: copper, zinc or galvanized strips help stop new growth over time.
It prevents regrowth. It will not clear moss already there.
Sources: IKO, OSU Extension and ARMA. Check your own shingle maker’s instructions first, because other methods may void a limited warranty.
Why it grows
Why moss grows on shingle roofs
Moss needs shade and moisture. OSU Extension says the plant depends on shade to thrive, so the slopes that stay damp under trees are the ones that grow it first.
IKO explains why it matters for shingles. Moss holds water against the roof, slows drainage and can work its way under shingles, lifting them. That uplift gives water a path into the layers below.
OSU also notes that moss can look dead in dry weather and recover after one rain. Dry moss is not gone moss.
Dark streaks on a roof are often algae, not moss. ARMA says algae discoloration should not be confused with moss, and that it typically shows as streaks rather than localized clumps.
Safe removal methods
How to remove moss from a roof safely
Based on IKO’s step-by-step method. Work from a ladder where you can.
Set up safely and spray the moss
Place the ladder on stable ground near the moss. Spray a moss-specific cleaner, or a homemade mix, onto the moss. IKO advises not stepping on the roof for this job.
Leave it for the label time
Follow the cleaner’s instructions. For a homemade spray, IKO says to leave it on for 15 to 20 minutes.
Rinse at low pressure
Use a garden hose on low pressure. Do not aim a pressurized spray under the shingles, because it can lift them and create a leak. Rinse off all the cleaner.
Lift off what has loosened
Gently lift loosened moss into a garbage bag clipped to the ladder, keeping one hand on the ladder.
Stop if it will not come off
If moss is still stuck, do not reach for a brush or a pressure washer. IKO says to ask a professional roofer what to do next.
What not to do
Roof moss removal mistakes that damage shingles
Do not use a power washer
ARMA says high-pressure washing is likely to damage asphalt roofing. IKO adds that it can break the shingle adhesive and strip granules.
Do not scrub or sweep
ARMA names brushes and brooms. IKO says scrubbing is likely to damage asphalt shingles and remove their granules.
Do not overdo the bleach
IKO warns that high concentrations of bleach and other chemicals may permanently damage shingles. ARMA notes bleach makes the roof slippery.
Do not climb a wet roof
OSU Extension and ARMA both advise caution. ARMA recommends that only trained professionals work on a roof.
Cost
What roof moss removal costs
We are not putting a dollar figure on it, because we could not source one we trust. The price moves with four things: roof size and pitch, how thick the moss is, whether the work is DIY or hired, and the method.
If you do it yourself, the cost is the cleaner, a sprayer and a ladder. Our best roof cleaner guide compares products and lists prices with their sources.
Lamar Homes does not list moss removal as a service. We do offer a free roof inspection, which tells you whether moss has already damaged the shingles.
Preventing regrowth
How to stop moss growing back
Let the sun in
OSU Extension calls trimming nearby trees the most effective long-term fix. As Jay Pscheidt of OSU puts it, you have to let the sun in or the moss will return.
Add a metal strip
IKO says a copper, zinc or galvanized strip at the ridge can stop moss, algae and lichen over time. It works on new growth only.
Keep gutters clean
IKO says roofers should inspect and clean gutters at least yearly, because backed-up water attracts moss.
When to call a roofer
When to call a roofer about roof moss
Call when the moss is thick, the roof is steep or wet, or you can see shingles lifting. IKO says a severe infection may mean replacing shingles the moss has damaged.
Our roof inspection is free. A GAF Certified inspector photographs what is there and gives you a written report. If shingles are damaged, our roof repair team can fix them.
Thinking about the roof’s age as well? Our guide on how long a roof lasts helps you judge whether to repair or replace.
Methods that go beyond the maker’s instructions may void a limited warranty, per IKO.
Pick the gentlest cleaner that works
Start with a bleach-free moss-specific cleaner. Avoid zinc sulfate if you have copper gutters or flashing.
Keep pressure and brushes off the roof
Use a low-pressure hose only, and rinse all cleaner off.
Plan the long-term fix
Trim shade, add a ridge strip and clean the gutters.
Questions
Roof moss removal questions
How much does it cost to remove moss from a roof?
It depends on roof size, pitch, how thick the moss is and whether you do it yourself or hire someone. Doing it yourself costs the price of a cleaner and a sprayer. We do not publish a professional price because Lamar Homes does not list moss removal as a service.
Is bleach or vinegar better to kill moss?
The manufacturer sources we checked describe diluted bleach, not vinegar. IKO gives a mix of two cups of chlorine bleach to two gallons of water, but warns that high concentrations can permanently damage shingles. A moss-specific cleaner that is bleach-free is IKO's first choice.
Does dish soap kill roof moss?
IKO lists a mix of eight ounces of dish soap in two gallons of water as a homemade option, left on for 15 to 20 minutes and then rinsed at low pressure. A moss-specific cleaner is the safer first choice.
What time of year should I put moss killer on my roof?
None of the manufacturer or extension sources we checked gives a calendar date. Follow the product label for temperature and rain, and plan around a dry spell with a gentle rinse, since cleaner left on the shingles can damage them.
Can I pressure wash moss off my roof?
No. ARMA, the shingle makers' trade body, says not to use a power washer, a brush or a broom on a roof. IKO warns that pressure can break the shingle's adhesive and strip its granules, and can cause leaks.
Will moss grow back after I remove it?
It can. Moss depends on shade and moisture, so OSU Extension says the most effective long-term fix is more sunlight on the roof, such as trimming nearby trees. A metal strip at the ridge helps prevent new growth but will not clear existing moss.
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