If you see black streaks (Gloeocapsa magma) or moss on your roof in What is soft wash roof cleaning and do I need it?, a soft wash is necessary. This process involves applying a specialized treatment at low pressure—no more than a garden hose—to kill organic growth. This is the only method recommended by the Asphalt Roofing Manufacturers Association (ARMA) to clean shingles without voiding your warranty.