Three different organisms colonize Northeast Ohio roofs, and they are not equally dangerous. Here is how to tell which one you have from the driveway, and how quickly each needs attention.
Black Streaks: Algae
What it looks like: dark gray or black streaks running down the slope, usually worst on the north-facing side.
What it is: gloeocapsa magma, an airborne algae that feeds on the limestone filler in asphalt shingles. The streaks are its dark protective coating.
How urgent: moderate. Algae will not destroy your roof this season, but it slowly consumes shingle material, holds heat and moisture, and it spreads. It is also the single biggest curb-appeal killer we see. The fix is a soft wash roof cleaning; never high pressure, which strips the granules that protect the shingle.
Green Carpet or Fuzz: Moss
What it looks like: thick green patches, often along shaded edges and in the gaps between shingles.
What it is: a true plant with root-like structures that work under shingle edges.
How urgent: high. Moss is the one that damages roofs mechanically. It lifts shingle edges as it grows, which lets wind and water get underneath, and it holds moisture against the roof deck like a wet sponge. Left alone through freeze-thaw winters, moss shortens a roof’s life measurably. If you can see green from the street, it is time.
Crusty Gray-Green Patches: Lichen
What it looks like: flat, crusty, coin-sized rosettes bonded tightly to the shingle surface.
What it is: a partnership of fungus and algae that anchors directly into the granule layer.
How urgent: moderate to high, and the most stubborn of the three. Ripping lichen off dry takes shingle granules with it. Proper treatment kills the organism so it releases and weathers away over the following weeks; patience beats force here.
The Common Thread
All three problems get worse every season they are ignored, and all three have the same safe answer: a low-pressure soft wash with the right solution, done from the ladder and the roof by people insured to be up there. It costs a small fraction of early roof replacement, and insurers have been known to take notice of heavily mossed roofs at renewal time.
Not sure which one you have? Text a photo to (440) 771-1889 and we will identify it and quote it. All-Star Power Cleaning is rated 5 stars by 300+ Google reviewers across Greater Cleveland.
