Drive through any Tulsa neighborhood more than ten years old and you'll see them: dark streaks running down asphalt shingle roofs, usually worst on the north-facing slope. That isn't dirt, soot, or 'weathering.' It's a living organism called Gloeocapsa magma — an airborne algae that lands on your roof and starts eating it.
Asphalt shingles contain limestone filler, and that limestone is exactly what the algae feeds on. As it spreads, it holds moisture against the shingle surface, degrades the protective granules, and raises the roof's temperature by darkening it.
Why Oklahoma roofs have it worse
Gloeocapsa magma thrives on humidity and warmth, and Tulsa summers provide both in abundance. Shaded roof slopes — under the mature trees common in South Tulsa, or any north-facing section that never fully dries — give the algae everything it needs. Once one roof on a street has it, spores spread to the neighbors on the wind.
Never let anyone pressure wash your roof
This is the most important sentence in this article: high-pressure washing destroys asphalt shingles. The granules embedded in each shingle are its UV and weather protection, and a pressure washer strips them off by the thousands. The roof looks clean for a season and then fails years early. Many shingle warranties are explicitly voided by pressure washing.
The correct method is a soft wash: a low-pressure application of professional cleaning solutions that cleans off the black streaks, followed by nature doing the rinsing. No high pressure touches the shingles. The roof keeps improving for a few weeks as rain rinses away what the solution loosened.
How to slow it coming back
- Keep gutters clear so moisture isn't pooling at the roof edge
- Clean at the first sign of streaking — early cleanings are smaller jobs
Hydra Total Care roof soft washes start at $500, priced by roof size and pitch, with before-and-after photos on every job. If your roof has streaks, send a photo to (918) 922-9348 and we'll tell you exactly what it needs.