What chemicals are used to clean roofs?

Roof cleaning is done to remove moss, lichen, algae, and buildup of other grime and dirt. There are several methods for roof cleaning, which can include a chemical soft wash, pressure washing, low-pressure washing and hand washing. When a chemical soft wash is used, a bleach mixture is sprayed onto the roof. The bleach-based solution is absorbed by the algae or moss, which dies from exposure to the chemical. The roof is then sprayed with a low-pressure rinse of water, which loosens the now-dead material, allowing it to slide off the roof.

For homeowners, the Asphalt Roofing Manufacturers Association recommends a mixture of 50 percent laundry-strength liquid chlorine bleach and 50 percent water. Professional roof cleaning companies will use an industrial mixture that is still safe but may be more effective in eliminating algae and moss growths. Asphalt shingle roofs are the most common type of roof, but each roofing material will have its own cleaning needs, so it’s best to consult with your roofing pro before diving in. Don’t do it yourself unless you can safely navigate your roof, the chemicals and a sprayer system. When in doubt, leave it to the pros.