How do I clean the black stain off my roof?
The black stain that grows and spreads on a roof is typically algae. PABCO® recommends cleaning algae from your roof by killing it with an application of a 50:50 mix of liquid chlorine bleach and water. This is sprayed onto the surface of the algae with a low pressure sprayer, like a garden weed sprayer. Allow the solution to dwell on the surface (15 to 20 minutes) and then rinse thoroughly with low pressure water.
Do not use abrasive cleaning methods such as pressure washing or the use of a brush or broom.
See the PABCO® Technical Bulletin on Recommended Maintenance Practices for additional details and related information.