What do you recommend for removing moss from roof composite shingles in the least toxic way? I have disconnected all downspouts and storm water from roof now flows into rain gardens planted with NW natives; rushes, sedges, Oregon Grape, ferns, Ocean Spray, Mock Orange, Monkey Flower, etc. moss is present on north side of roof which I want to remove. I read that zinc sulfate may damage plants.
Getting rid of moss doesn’t rely on chemicals, alone. Instead, it begins with some old fashioned physical activity to remove it with a brush or broom. After moss is removed, consider applying a thin application of protective material which helps limit moss development temporarily.
- Begin by removing the moss using with either a standard bristle scrub brush or a stiff broom.
- Don’t use any sort of high-pressure device because they degrade roof quality and longevity by removing some of the gravel layer added to the roofing during the manufacturing process.
- After the moss has been removed, apply a commercial product which slows moss development but, at the same time, realize that nothing lasts forever. In general, it’s easier to apply liquids more evenly than powders.
- Thin out, or remove, any vegetation overhanging or shading the roof as another preventive measure; repeat as needed.
- These measures can be dangerous, due to the slippery surface of the roof where there is moss or algae. Carefully consider the hazards before taking on this job, and seek professional assistance when needed.
Resources for you:
- “Chemical Moss Control for Roofs, Decks, and Sidewalks” compares the most common moss removal products.
- “Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems”