Those dark streaks running down your roof aren't dirt, and they won't rinse off in the rain. Here's what's really going on up there.
It's algae — and it's eating your shingles
The culprit is a hardy blue-green algae called Gloeocapsa magma. It feeds on the limestone filler in asphalt shingles and spreads across the roof as dark streaks, usually worst on the shaded, north-facing side. In the humid Upstate climate, it thrives.
Why it's more than an eyesore
Beyond looking neglected, the algae holds moisture against the shingles and reduces how much sunlight the roof reflects — meaning more heat and more wear. Left alone for years, it shortens the life of the roof you paid a lot of money for.
Don't let anyone pressure wash it
High pressure strips the protective granules right off asphalt shingles and can void your warranty. The correct fix is a no-pressure soft wash: a cleaning solution applied at low pressure that kills the algae and lifts the staining without ever touching the shingles hard. The streaks disappear; moss and lichen release naturally over the following weeks.
If your roof has that streaky look, it's worth treating before it spreads. See our roof washing service or request a free quote below.