What is the best roof cleaner for moss?
Short answer. The best approach is a moss killer labeled for roofs, such as products based on zinc compounds or potassium salts of fatty acids, applied at low pressure and left to work so the dead moss can be brushed or rinsed off gently. Avoid pressure washers and stiff scraping, which strip granules and shorten the shingle's life.
Types of moss cleaners
- Zinc based moss killers: kill moss and leave a residue that slows regrowth. Can stain some surfaces and are hard on nearby plants and metal if overused.
- Fatty acid soaps (potassium salts): gentler, work fast on moss, with less residue. May need repeat applications.
- Diluted bleach solutions: better on algae streaks than thick moss. Hard on landscaping and can discolor some materials, so rinse plants before and after.
- Oxygen based cleaners: gentler on plants, slower acting, used by some cleaners for algae and light moss.
How to use any of them safely
- Read and follow the label; many moss killers are regulated products with specific rates.
- Apply with a garden sprayer, not a pressure washer.
- Give it time. Dead moss loosens over days or weeks.
- Brush gently downhill with a soft brush, never against the shingle laps.
- Protect plants and pets, and keep runoff out of ponds and streams.
The shingle manufacturer's view
Check your shingle maker's cleaning guidance, since harsh methods can affect warranty coverage. Industry guidance generally favors low pressure application and rinsing.
Stop it coming back
Trim branches, keep valleys clear and consider zinc or copper strips near the ridge. Do not walk on a wet, mossy roof; it is extremely slick. Read moss and lichen on roofs and trees and your roof.