If you live in Central Maine, take a walk outside and look up at your roof, especially the north-facing side. See those long, dark streaks running down your shingles? You’re not alone. Drive through any neighborhood in Bangor, Brewer, Hampden, or Hermon, and you’ll spot them on house after house.
Most homeowners assume those streaks are dirt, soot, or just “an old roof.” Some are told they need a full roof replacement. The truth is usually much better news and much cheaper to fix.
I’m the owner of Northeast Softwash, a roof and exterior cleaning company based in Bangor, Maine, and in this post I’ll explain exactly what those streaks are, why Maine homes get them so badly, whether they’re actually damaging your roof, and the safe way to remove them (hint: it’s not a pressure washer).
The Black Streaks Are Alive. Here’s What They Actually Are
Those dark stains are a type of airborne algae called Gloeocapsa magma. It lands on your roof, takes hold, and feeds on the crushed limestone filler inside modern asphalt shingles. As the algae colony grows and dies off, it builds up a dark, protective outer layer — that’s the black streaking you see.
Because it’s a living organism and not just dirt, it doesn’t wash away in the rain. It actually thrives in moisture, which is exactly why it spreads in streaks: it follows the path water takes down your roof.
You’ll usually notice it worst on the north side of the house and in shaded areas, where the roof stays damp longer after rain, dew, and snowmelt.
Why Maine Roofs Have It So Bad
Roof algae shows up all over the country, but Central Maine gives it nearly perfect conditions:
- Long, damp seasons. Between spring rain, humid summers, fall moisture, and months of melting snow, Maine roofs spend a huge portion of the year wet.
- Tree coverage. Our wooded lots mean shade, and shade means roofs that never fully dry out. Overhanging trees also drop debris that holds moisture and feeds moss and lichen.
- Older housing stock. Many homes in Bangor, Hampden, and Hermon have roofs that are 10, 15, or 20+ years old — plenty of time for algae, moss, and lichen to establish.
If your home backs up to woods or sits under mature trees, you’re a prime candidate. It’s not a reflection of how well you maintain your home; it’s biology and weather.
Is It Actually Hurting Your Roof, or Just Ugly?
Both, unfortunately. In the early stages, algae staining is mostly a curb-appeal problem but left alone for years, it becomes a roof-health problem:
- It eats your shingles. The algae literally feeds on the limestone in your shingles, slowly breaking them down.
- It holds moisture against the roof. A colonized roof stays wetter longer, which accelerates wear — a real concern in a state with our freeze-thaw cycles.
- It invites moss and lichen. Algae is often the first arrival. Moss and lichen follow, and lichen in particular anchors into shingles and pulls granules loose when it’s ripped off.
- It can raise cooling costs. Dark staining absorbs more heat than clean shingles.
- It can affect insurance and home sales. A heavily stained roof photographs like a failing roof. Some insurers flag it, and buyers negotiate against it — even when the roof underneath is structurally fine.
The good news: if your shingles aren’t already at the end of their life, cleaning restores both the look and the healthy condition of the roof for a small fraction of the cost of replacement.
Why You Should Never Pressure Wash a Roof
Here’s where a lot of homeowners (and unfortunately, some “pressure washing guys”) get it wrong. Blasting asphalt shingles with high pressure:
- Strips the protective granules that give shingles their weather resistance and lifespan
- Can force water under the shingles and into your roof deck
- Can void manufacturer warranties — most shingle manufacturers explicitly warn against pressure washing
- Doesn’t kill the algae. It knocks off the visible layer, and the streaks come back fast because the organism is still alive.
A roof is one of the most expensive components of your home. High pressure is the wrong tool for it, full stop.
The Right Way: Soft Washing
Soft washing is the method recommended by the Asphalt Roofing Manufacturers Association. Instead of pressure, it uses a low-pressure application — about the force of a garden hose — to apply a professional cleaning solution that kills the algae, moss, and lichen at the root.
Here’s what that looks like when we clean a roof in Bangor, Hampden, or Hermon:
- Inspection first. We look at shingle condition, roof age, and what’s actually growing up there.
- Protect the property. Plants, landscaping, and surfaces around the home are pre-wetted and rinsed throughout the process so the cleaning solution never harms them.
- Low-pressure application. The solution is applied gently across the roof, where it kills the algae on contact. No blasting, no granule loss, no walking damage.
- The transformation. Streaks begin disappearing immediately. Heavier moss and lichen die off and release from the roof naturally over the following weeks with rain — without tearing shingles apart.
Because soft washing kills the organism instead of just knocking the color off, the results last for years rather than months.
How Much Does Roof Cleaning Cost in Maine?
Every roof is different — size, pitch, height, and how heavy the growth is all factor in but a professional soft wash roof cleaning typically runs a few hundred dollars for an average home. Compare that to $10,000–$20,000+ for a roof replacement, and cleaning is one of the highest-return maintenance projects a homeowner can do.
We provide free, no-pressure quotes, and in most cases we can quote from photos or a quick drive-by without you needing to be home.
xterior gutter brightening), and wash decks, fences, and concrete throughout Central Maine.
Roof Cleaning in Bangor, Hampden & Hermon
Northeast Softwash is a locally owned, licensed, and insured exterior cleaning company based in Kenduskeag. We proudly serve Bangor, Hampden, and Hermon along with Brewer, Orono, Old Town, Glenburn, Levant, Corinth, and the surrounding Central Maine communities. If your roof has black streaks, moss, or lichen — or you’re just not sure what you’re looking at send us a photo. We’ll tell you honestly whether it needs cleaning, and we’ll never try to sell you a wash your roof doesn’t need.
