Will Pressure Washing Damage My Roof? What Shingle Manufacturers Actually Say
By Kenny Monks, owner of Rooted Exterior Solutions · Updated September 2026
Short answer: yes. Pressure washing an asphalt shingle roof strips the protective granules off the shingles and can shorten the roof's life. The Asphalt Roofing Manufacturers Association (ARMA), the trade group for the companies that make the shingles, says never to use a pressure washer on an asphalt shingle roof. The safe way to remove black streaks, algae and moss is a low-pressure soft wash.
What do the black streaks on my roof mean?
Those dark streaks are algae, usually a type called Gloeocapsa magma. It feeds on the limestone filler in asphalt shingles and grows best where a roof stays damp: the north side, valleys and anywhere trees hang over. Around Augusta, with about 45 inches of rain a year and humid summers, we see it on roofs only a few years old.
It isn't just cosmetic. Algae, and the lichen and moss that follow it, hold moisture against the shingles.
Why does pressure washing hurt shingles?
Every asphalt shingle is covered in small ceramic-coated granules. They shield the asphalt from the sun. High-pressure water knocks those granules loose, and once they're gone they don't grow back. The shingle underneath then breaks down faster in the sun.
ARMA puts it plainly: using a pressure washer on an asphalt shingle roof "will cause granule loss" and likely premature failure of the roof. High pressure can also lift shingle edges, force water under them and void your manufacturer's warranty.
There's a second problem. Pressure washing only knocks off what you can see. The algae's roots stay in the shingle, so the streaks come back fast.
What do manufacturers recommend instead?
ARMA recommends a cleaning solution applied at low pressure, left to dwell long enough to kill the growth, then rinsed at low pressure. In the industry, that's called a soft wash. The solution does the work, not the water pressure.
Here's how we do a soft wash roof cleaning at Rooted:
Pre-wet your plants and landscaping so the solution can't soak in.
Apply the cleaning solution at low pressure.
Let it dwell long enough to kill the algae, lichen and moss at the root.
Rinse the roof and your plants again at low pressure.
Because the growth is killed instead of blasted, a soft-washed roof stays clean much longer. Every soft wash roof cleaning we do comes with a 3-year guarantee.
How can I tell if a roof cleaner is doing it wrong?
Ask these before you hire anyone:
"Do you use a pressure washer on the roof?" The only acceptable answer is no.
"What do you do to protect my plants?" Look for pre-wetting and rinsing.
"Are you insured?" Roof work needs general liability coverage.
"Do you guarantee the results?" A company that kills the algae instead of blasting it can stand behind the result.
If you see someone on a roof with a pressure wand and a surface cleaner, that roof is losing granules.
Can I clean my own roof?
We don't recommend it. It means working at height on a slippery, wet surface, and getting the mix and dwell time wrong can leave streaks or hurt your plants. If you're set on it, never use a pressure washer, and follow ARMA's guidance.
Frequently asked questions
Does soft washing void my shingle warranty?
No. It follows the method the roofing manufacturers' own trade group recommends. Pressure washing is what puts a warranty at risk.
How long does a soft wash roof cleaning last?
Ours come with a 3-year guarantee. Beyond that, it depends on how much shade the roof gets.
Is it safe for my plants and pets?
Yes, when it's done right. We pre-wet and rinse plants, and pets should stay inside until everything has been rinsed.
Can you clean metal or tile roofs?
Yes. Metal and tile roofs are soft washed too.
Rooted Exterior Solutions soft washes roofs across the CSRA, including Augusta, Evans and North Augusta. Call or text Kenny at 803-220-1722 for a free quote.
Source: Asphalt Roofing Manufacturers Association, "Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems," asphaltroofing.org.
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