Can you use bleach as a roof moss cleaner?
Short answer. Yes, a diluted household bleach solution kills roof moss and lightens stains, but it does not make thick moss fall off by itself. You still need to wait for the dead moss to loosen and remove it gently, and you must protect plants, gutters and yourself from the bleach.
How bleach works on moss
Sodium hypochlorite kills moss tissue on contact and bleaches the green color. Thin moss may wash away within days. Thick cushions die from the outside in and can need a second application before the base lets go.
Mixing and applying
- Use plain, unscented household bleach diluted with water, about one to one as roofing manufacturers describe for algae, or as your shingle maker directs.
- Apply with a pump sprayer at low pressure on a cool, cloudy day.
- Rinse according to the shingle maker's guidance, then flush gutters.
Protecting plants and property
- Soak plants before and after, and cover them during application.
- Rinse siding, decks and metal promptly; bleach spots and corrodes.
- Do not let runoff reach ponds, creeks or storm drains.
- Never mix bleach with ammonia, vinegar or other cleaners.
Removing what is left
Once the moss is brown and loose, push it off by hand or with a soft brush, working downslope. Do not pressure wash. Clumps left in gutters should be scooped out so they do not clog downspouts.
Bleach versus other moss killers
Bleach is fast and cheap but offers no lasting protection. Zinc based treatments and zinc or copper strips work more slowly but slow regrowth. Many homeowners use bleach for the first cleanup and strips for prevention. See moss and lichen on roofs and black streaks and algae on roofs.