If you notice patches of green growing on your asphalt roof, moss is likely the culprit. Moss grows on spots on the roof where there is not an ample amount of sunshine. Removing roof moss is necessary in preserving both the appearance and structure of the roof. Over time, moss will spread and begin to eat away at the shingles. Oxygen bleach or chlorine bleach are used to clean moss from a roof. It is best to try the oxygen bleach method first; oxygen bleach is eco-friendly and will not cause damage to the surrounding landscaping or to the roof itself.
Using Oxygen Bleach
Fill a clean, empty garden sprayer with 1 gallon of hot water. Add 6 oz. oxygen bleach to the water. Wait about five minutes for the oxygen bleach to dissolve into the water.
Spray the solution onto the moss-stained shingles. Allow the solution to remain on the shingles for at least 20 minutes. If you notice the solution starting to dry, apply more to the roof. The goal is to keep the shingles wet with the oxygen bleach mixture for at least 20 minutes.
Scrub the shingles lightly with a long-handled scrub brush. The moss will come off easily.
Rinse the shingles with plain water from the garden hose. Rinse from the top of the roof downward.
Repeat this process, if necessary. Depending on the severity of the moss growth, several applications may be required to remove all of the moss.
Using Chlorine Bleach
Fill a clean, empty garden sprayer with equal parts chlorine bleach and warm water. Shake the sprayer to combine the ingredients.
Saturate the asphalt shingles with the mixture. Allow the bleach mixture to sit on the shingles for at least five minutes but for no more than 30 minutes. If the bleach mixture begins to dry, apply more.
Scrub the moss-stained shingles with a long-handled scrub brush to loosen the moss. Rinse the roof with water from the garden hose, working from the top down.
Repeat this process, if necessary. It may take more than one application to remove all of the moss from the roof.