How to Remove Algae from Your Roof in Utah

Black roof streaks may be algae rather than mold or a failing roof. Identify the material and the discoloration, then choose manufacturer-compatible professional cleaning instead of pressure washing or scraping shingles.

1. Identify the stain and the covering

ARMA describes algae discoloration that can be mistaken for mold. Moss is a different growth. A dark streak does not establish structural failure, so identify the issue and the roof material before choosing treatment.⁠^[1]⁠^[2]

2. Use compatible professional cleaning

For asphalt shingles, ARMA rejects power washers, brushes and brooms for algae cleaning. Other methods or chemicals need the shingle manufacturer’s approval. Do not use an unexplained treatment time or a universal chemical recipe.⁠^[2]

Safe access, people, plants and runoff also need planning. Do not climb onto the roof to scrape, spray or test the surface.

3. Reduce recurring moisture and debris conditions

Arrange appropriate vegetation and drainage maintenance. Ask whether any proposed metal strip or product is compatible with the roof; it is not a guarantee that growth cannot return.

Separate appearance from active leaks, damaged covering or indoor moisture. Those concerns may need a different diagnosis.

Questions for an assessment

• Which growth and roof material are present?
• What does the manufacturer permit?
• How are access and runoff managed?
• Is cleaning the main issue, or is repair or moisture investigation needed?

Use the assessment questions when describing the concern.