Your Roof Is Hosting Something — Time to Shut It Down
Moss, lichen, and streaks aren’t just cosmetic. Learn how soft washing removes the growth without damage — and why Maine’s most common roof problems have nothing to do with shingles.
When people notice black streaks, blotches, or thick green patches on their roof, they often assume it’s just surface dirt — or that their roof is nearing the end of its life. In reality, those signs almost always point to living growth: things like algae, lichen, and moss that feed on roofing materials and hold on to moisture.
In Maine and other parts of New England, it’s common for roofs to show both staining and moss coverage — and soft washing is the method designed to deal with both.
Let’s break down how roof soft washing works, what manufacturers like CertainTeed have to say about it, and what kind of results homeowners should expect.
Stains, Moss, and the Biology of a “Dirty Roof”
Those black streaks? That’s a bacteria called Gloeocapsa magma, and it feeds on the limestone filler in asphalt shingles. It creates a dark, damp layer that holds in heat and spreads quickly.
But the problem doesn’t stop there. In shaded or damp areas — especially on the north side of a roof — you'll often find moss, lichen, and even algae. These organisms:
Grow roots or tendrils that embed into the shingle surface
Hold moisture against the roof 24/7
Accelerate granule loss, shingle deterioration, and in some cases, even lead to leaks or rot
How Soft Washing Treats Moss and Lichen
Soft washing doesn’t just remove surface dirt — it’s a biological treatment that kills moss, algae, and lichen at the root.
The sodium hypochlorite (SH) solution works by breaking down the cellular structure of the growth and sterilizing the surface. Unlike pressure washing, which might blast the top layer off but leave roots behind, soft washing kills the entire organism without causing physical damage to the shingles.
Here’s what to expect:
The green fades quickly, but the moss doesn’t vanish instantly
Moss, lichen, and other organic growth will begin to dry out, turn white/yellow, and die within a few hours
Over the next weeks or months, it naturally detaches and washes away with the rain
There’s no scraping, no brushing, and no risk to the shingles
Instead of blasting growth away, we let the chemistry do the work — slow and steady, no worries, no damage.
Roof Manufacturers Provide Cleaning Specs — And They're Very Clear
Major manufacturers — like CertainTeed, GAF, and Owens Corning — all specify that the only approved method for roof cleaning is low-pressure soft washing using an SH-based solution and surfactants.
They explicitly advise against:
High-pressure washing
Scrubbing or brushing
Abrasive tools or agitation
This guidance is echoed by the Asphalt Roofing Manufacturers Association (ARMA). Ignoring these guidelines can actually void your roof’s warranty, which is why it’s important to use the method your roofing system was designed to handle.
Soft washing is the safest and most effective treatment available — a gentle reset for one of your home’s most important features.
SH Alternatives? They Exist — But With Limitations
There are bleach-free options out there, like sodium percarbonate, often marketed as “eco-friendly” or “non-chemical.” These are oxygen-based and can be effective on light algae or mildew, but they:
Are much less effective on moss and lichen
Often require agitation, brushing, or multiple applications
Aren’t listed or recommended by major shingle manufacturers for this purpose
If your roof has moss — or if you live in an area with heavy shade and tree coverage — SH-based soft washing is the safest and most effective treatment available.
Why You Should Also Wash What’s Beneath the Roof
When you wash a roof, you’re also — by default — washing everything beneath it. Gravity guarantees that the soft wash solution will drip down and contact:
Windows and siding
Trim and doors
Deck railings, porches, and patios
If those areas are already dirty (or never washed), you're going to see uneven drip trails, bleach spots, and rinse marks unless they’re cleaned as part of the same service.
That’s why most roof wash projects should include a house wash, too. It’s not about upselling — it’s about doing the job the right way and leaving the home looking consistently clean, top to bottom.
It’s not just about keeping up appearances — it’s about showing love to your space, the same way you care for what’s inside.
Soft Washing Is About Safety and Long-Term Care
Beyond appearance, soft washing is the safest way to care for your roof and your property:
For your roof: No granule loss, no lifted shingles, no abrasion
For your home: No harsh runoff, no mess on your siding or decks
For your landscaping: Proper plant protection, pre-soaks, post-rinses, and neutralization procedures
A good soft wash company isn’t just spraying a roof — they’re thinking about every surface the solution will touch and every detail of safety on-site.
When Done Right, the Results Speak for Themselves
A professionally soft-washed roof:
Looks cleaner right away, with full visual improvement over the next 1–2 months
Stays cleaner longer, often 3–5 years or more, depending on environment and maintenance
Helps you avoid unnecessary replacement by addressing what’s actually a cleaning issue — not a failure of materials
Your roof protects everything beneath it — we just help it get back to feeling clean, strong, and steady again.
Final Thought: You Don’t Have to Replace It — You Might Just Need to Clean It
In Maine, mossy roofs are common — but that doesn’t mean you need to live with them. You also don’t need to replace a roof just because it looks bad. In many cases, it just needs to be treated the right way, with a little patience and the right understanding.
Soft washing restores more than just curb appeal — it protects your roof’s lifespan, your home’s health, and your peace of mind.
At the end of the day, your roof takes the brunt of sun, rain, wind, snow, and time. When it’s cleaned with care and treated the right way, you can feel good knowing your home is breathing easy again — and that everything’s alright, top to bottom.