Remove moss from a roof using a brush to scrub it away. Then, follow with a bleach and water spray treatment on the roof to kill any remaining moss or algae, and add a 6-inch copper strip under the top row of shingles, to prevent its return.
Before spraying the roof with bleach, water the areas of landscaping where the bleach might drip, then mix the spray with equal parts of laundry bleach and water and apply it with a garden sprayer. After applying the bleach, use a garden hose to wash away the bleach from plants.
While pressure washers remove moss from the roof, the high pressure from the wand has the potential to damage the shingles and cause leaks. Gentle hand brushing is effective and less likely to cause damage, although it requires more time.
Moss is more likely to grow on the shaded side of the roof. The materials stay wet, providing a place for the plant to take root. As it continues to grow, it causes damage to the roof by lifting shingles, so it becomes more difficult for water to drain. With early intervention, you can prevent permanent damage to the home. Installing the metal strip at the top of the house provides many years of protection against growth.