What Causes Dark Roof Streaks
The dark streaks you see spreading across roofs throughout DFW neighborhoods are caused by gloeocapsa magma — a type of cyanobacteria that feeds on the limestone aggregate in asphalt shingles. The bacteria grows in colonies that appear as dark gray to black streaking, typically beginning on shaded, north-facing slopes where moisture retention is highest.
Left untreated, the bacteria spread progressively across the entire roof surface, absorbing heat and accelerating UV degradation of shingles. Insurance companies and roofing manufacturers recognize extensive biological growth as a contributing factor in premature shingle failure.
The Only Manufacturer-Approved Removal Method
The Asphalt Roofing Manufacturers Association (ARMA) recommends low-pressure soft washing with a sodium hypochlorite solution as the safe removal method. High-pressure roof washing strips granules from asphalt shingles and voids most manufacturer warranties — it must be avoided.
Blues Home Services uses ARMA-compliant soft washing for all DFW roof cleaning. We apply biodegradable algaecide at low pressure, allow appropriate dwell time for the chemistry to kill biological growth at the root, and include a post-treatment application. The results are immediately visible — and the algaecide continues working after we leave.