Black roof streaks caused by Gloeocapsa magma are removed through soft washing: applying a sodium hypochlorite and surfactant solution to the roof surface at low pressure (100 to 300 PSI), allowing adequate dwell time for the chemistry to kill the bacteria, and then rinsing gently. This method kills the organism and removes the dark staining without damaging shingles. Pressure washing is not recommended by ARMA (the Asphalt Roofing Manufacturers Association) and should not be used on asphalt shingles.
Why the method matters so much
The black streaks are produced by Gloeocapsa magma, a cyanobacteria that protects itself with a dark pigmented outer coating. Pressure washing can blast the visible staining off the shingle surface but does not reliably kill the organism, and the mechanical force of 2,000 to 4,000 PSI removes the protective granule layer from asphalt shingles. Those granules protect the asphalt binder from UV degradation. Once granules are removed, shingle deterioration accelerates rapidly. Soft washing kills the bacteria with chemistry and rinses at pressure too low to displace granules.
Step-by-step: how a professional soft wash removes roof streaks
A professional roof soft wash follows this general process:
- Pre-wet and protect landscaping: The areas below the roof edge are pre-rinsed with plain water, and sensitive plantings are shielded.
- Apply soft wash solution: A mixture of sodium hypochlorite, surfactant, and water is applied from the ridge down using low-pressure equipment (100 to 300 PSI). The surfactant helps the solution cling to the shingle surface.
- Allow dwell time: The solution remains on the surface for the time needed to oxidize and kill the Gloeocapsa magma organisms. This varies based on concentration and severity.
- Rinse at low pressure: The roof is rinsed at low pressure. Dead bacteria and staining material wash away during this phase.
- Post-rinse landscaping: The surrounding area is rinsed again to remove any chemistry runoff from plant surfaces.
What results to expect
Immediately after a soft wash, most black staining will be gone or significantly reduced. Some older, heavier staining may require a second treatment or may leave slight ghost staining that continues to lighten over the next several rain cycles. The bacteria is dead; the remaining discoloration is a residual pigment that weathers out. A roof that had full-coverage black streaking typically shows dramatic improvement in one treatment.
Will the streaks come back?
Yes, eventually. Gloeocapsa magma spores are airborne and will recolonize any roof surface over time. Soft washing does not prevent future colonization. In Fort Worth's climate, most cleaned roofs remain visually clear for two to four years before streaking returns to a level that warrants re-treatment. Homes with significant tree canopy may see regrowth sooner.
What about zinc strips and copper products?
Metal oxide compounds (zinc from galvanized metal or copper from copper-treated products) inhibit algae and cyanobacteria growth. Copper ridge strips installed during a roof replacement or after cleaning can extend the streak-free interval by releasing trace amounts of copper with each rain. These are not a substitute for cleaning an already-stained roof, but they can be useful as a maintenance measure after cleaning.
DIY soft washing: what to know
DIY roof soft washing is possible but carries real risks. Working on a roof slope is physically dangerous, especially when wet. Consumer-grade soft wash equipment may not apply the solution uniformly. Incorrect SH concentration can damage landscaping. If you are considering a DIY approach, the safety risks alone make professional service worth the cost on most roofs.
Schedule a roof cleaning with CARE
CARE uses a dedicated soft wash system for roof cleaning in Fort Worth and surrounding cities. No pressure wands are used on shingle surfaces. Call (945) 275-8031 or visit our roof cleaning page to schedule your roof soft wash.