Black streaks on commercial roofs are almost always Gloeocapsa magma — a hardy algae that thrives on shingle limestone. Cleaning is a curb-appeal issue and a warranty preservation issue. Done wrong, it voids manufacturer coverage.
Why Never Pressure Wash a Roof
High pressure strips shingle granules — the UV protection layer. Manufacturers explicitly void warranties for pressure-washed shingles. TPO and EPDM membrane roofs can be perforated. Metal roof paint systems are also damaged.
The Soft Wash Method
- Sodium hypochlorite plus surfactant.
- Applied via low-pressure sprayer (under 200 PSI).
- Dwell 15-30 minutes.
- Rinse with garden-hose pressure.
- Pre-wet and post-rinse all landscaping.
Warranty Verification
Manufacturers including GAF, CertainTeed, and Owens Corning have specific approved cleaning methods. Verify before cleaning. Some require licensed contractors to preserve warranty coverage.
Roof Cleaning Without the Damage
We soft-wash commercial roofs to manufacturer-approved standards, preserving warranty and extending service life.