Roof cleaning, done the way that does not wreck your roof
The method matters more than the company. We explain why low-pressure washing is the accepted approach on asphalt, what a proper visit looks like, and when your roof does not need cleaning at all - then match you with local pros.
What is roof cleaning?
Roof cleaning removes the living growth - algae, moss, lichen - and the debris that sits on a roof surface. On asphalt shingles the accepted method is low-pressure ("soft") washing: a cleaning solution does the work and the water only rinses. The Asphalt Roofing Manufacturers Association's published guidance is explicitly non-pressure cleaning, and several shingle warranties treat high-pressure washing as damage rather than maintenance. Any company that answers "we pressure wash it" is the wrong company.
Signs you need roof cleaning
- Dark vertical streaks running down the north or shaded slopes - that is algae, and it spreads downward with the water
- Green cushions of moss sitting in the joints between shingles, especially along the shaded lower courses
- Crusty grey-green patches that look painted on and will not brush off - lichen, which roots into the surface
- Shingle edges beginning to lift where moss has grown underneath and wedged them up
- Granules collecting in the gutters or at the bottom of the downspout in quantity
- A pending home sale or appraisal where a streaked roof reads as "needs replacing" to a buyer who has not looked closely
Seeing something not on this list? Browse roof cleaning problems by symptom →
How roof cleaning actually works
Roof assessment from the ground and the ladder
Slope, roof material, age, brittleness of the shingles, what is actually growing, and whether the roof is safe to walk. A roof close to the end of its life may be cleanable but not walkable.
Watch forA quote given over the phone from a satellite image alone. Nobody can tell moss from lichen, or a sound shingle from a brittle one, on aerial imagery.
Protecting everything below the roofline
Cleaning solutions run off the roof and land on your planting, your lawn and your paintwork. Competent crews pre-wet and tarp landscaping, cover or divert downspouts, and rinse continuously.
Watch forNo mention of plants at all in the quote. Landscape damage from runoff is the most common complaint about roof washing, and it is entirely preventable.
Application at low pressure
The solution is applied with a low-pressure pump - closer to a garden hose than a pressure washer - so it sits on the growth long enough to kill it rather than blasting it off.
Watch forA pressure washer wand pointed at asphalt shingles, at any setting. It removes the granules that are the shingle's UV protection, and you will not see the damage for a year or two.
Rinse, and a realistic expectation of the result
A low-pressure rinse takes off the dead growth. Some staining continues to fade over the following weeks as rain carries away what is left, which is normal and not a sign the job was half-done.
Watch forBeing promised a like-new roof on the day. Heavy lichen in particular often leaves a shadow, and forcing it off mechanically costs you shingle surface.
Clearing the gutters last
Everything that came off the roof is now in the gutters. Gutter clearing belongs at the end of a roof wash, not before it - do it first and you pay for it twice.
What does roof cleaning cost?
Roof cleaning is usually priced per square foot of roof area or as a flat job price, and varies widely by region, roof pitch, access and how much growth there is. Steep and multi-storey roofs cost meaningfully more because of the access equipment. See the Cost Guide for current ranges.
See the full roof cleaning cost guide - by material, size and region →
If the number is the problem, here are the ways people pay for it →
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When roof cleaning is the wrong call
When saying yes is the wrong move:
- Your roof is within a couple of years of replacement anyway. Cleaning a roof you are about to tear off buys appearance and nothing else. If the shingles are curling, cracking or shedding granules heavily, put the money toward the replacement quote instead.
- The only company available insists on pressure washing asphalt. Waiting for a contractor who soft washes is strictly better than getting it done sooner by someone who will strip the surface. This is the one place where doing nothing beats doing it wrong.
- There is an active leak. A leak is a roofing repair, not a cleaning job. Washing a leaking roof pushes water at the exact area that is already failing. Get the leak fixed first.
- It is purely cosmetic and you are staying put. Light algae streaking is ugly but slow. Moss is the growth that genuinely damages a roof, because it holds water against the shingle and lifts the edges. If it is streaks only and nobody is looking, the urgency is low.
- The roof is too brittle to walk and the company has no ground-based method. Old, sun-baked shingles crack under foot traffic. If the only plan involves crew members walking every course, the cleaning can cost you more shingle life than the algae would have.
- You just had a full re-roof with algae-resistant shingles. Those have copper-bearing granules designed to suppress growth. Cleaning a two-year-old roof is money spent on a problem that has not arrived.
Types of roof cleaning
| Option | What it means for you |
|---|---|
| Soft wash roof cleaning | The low-pressure method itself - what is applied and why |
| Tile roof cleaning | Clay and concrete tile need a different technique entirely |
| Metal roof cleaning | Coated panels and the corrosion risk from the wrong solution |
| Method and material comparisons | Soft wash vs pressure wash, DIY vs professional, clean vs replace |
Can I do this myself?
Reasonable to DIY
- Clearing leaves and needles out of valleys and gutters from a ladder, without stepping onto the roof
- Trimming back the branches that are shading the roof - shade is what feeds the growth in the first place
- Applying a labelled, ready-to-use roof treatment from the edge with a hose-end applicator, following the product label exactly
Call a licensed pro
- Anything that requires walking on a wet, sloped or steep roof
- Two-storey roofs, where the ladder work is the real risk rather than the cleaning
- Heavy moss or lichen that needs solution dwell time and controlled rinsing
- Tile and metal roofs, where the wrong technique breaks tiles or damages the coating
What to check when hiring for roof cleaning
- Do you soft wash or pressure wash, and at what pressure on my roof material? The single question that separates the companies. On asphalt the answer should be low pressure with the solution doing the work. A vague answer is an answer.
- What will you do to protect my plants, lawn and siding from runoff? Runoff damage is the most common complaint. Pre-wetting, tarping and continuous rinsing should be described specifically, not promised generally.
- Are you insured for work at height, and can I see the certificate? If someone falls off your roof uninsured, that becomes your problem. Ask to be sent the certificate directly by the insurer or broker, not a photocopy.
- Will anyone walk on my roof, and how will you limit it? Foot traffic on hot or aged shingles causes damage. A crew that plans its access deliberately is a crew that has thought about it.
- What exactly does your warranty cover, and for how long? Many roof-cleaning warranties cover regrowth, not damage. Those are very different promises. Read which one you are being given.
- Will you check my shingle manufacturer's cleaning guidance before you start? Manufacturers publish cleaning instructions, and some treat pressure washing as damage that voids coverage. A professional will know or will look it up.
- Is gutter clearing included at the end, or billed separately? The growth you paid to remove ends up in the gutters. Settle this before the job, not when the invoice arrives.
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Sources
Sources last checked
- Asphalt Roofing — algae and cleaning contextARMARetrieved 2026-08-04Manufacturer/trade guidance on cleaning methods that void warranties.
- Occupational Employment and Wages — Construction TradesU.S. Bureau of Labor StatisticsRetrieved 2026-08-04Labor cost context for home-services trades nationally.
Sources for figures and claims on this page.
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