What is the best product to remove algae from a roof?
Short answer. For fast results, a diluted sodium hypochlorite (bleach) solution applied gently and rinsed is the most widely recommended approach for asphalt shingles. Oxygen bleach products are gentler on plants but slower, and spray and leave treatments work gradually over weeks with rain, so the best choice depends on whether you want speed or a lighter touch.
Compare by active ingredient, not brand
- Sodium hypochlorite (chlorine bleach). Kills algae and lightens streaks within minutes. Industry guidance for asphalt shingles commonly suggests a diluted bleach and water mix. Downsides: harsh on plants and grass, can discolor some metals and painted trim, must be rinsed.
- Sodium percarbonate (oxygen bleach). Breaks down into soda ash, water and oxygen. Gentler on landscaping, slower acting, often needs more dwell time or a second round.
- Quaternary ammonium "spray and leave" products. Applied once and left for rain to work in. Streaks fade gradually over weeks to months. Easy, but not instant.
- Zinc or copper. Strips installed near the ridge release metal ions with each rain, slowing regrowth below them. Prevention, not removal.
What to avoid
- Pressure washers, which strip granules.
- Mixing chemicals, especially bleach with ammonia based cleaners.
- Acidic cleaners not labeled for asphalt shingles.
- Iron based moss products, which can leave rust colored stains on shingles and concrete.
How to choose
If you want streaks gone this weekend and can protect plants, a gentle bleach wash. If plants and runoff are a concern, oxygen bleach. If the roof is steep and you would rather not climb, a leave on treatment applied from the eave, or a soft wash company.
For the full method, see black streaks and algae on roofs, and for thicker growth, moss and lichen on roofs.