Moss grows on all types of roofing, including wood, metal, asphalt, clay, concrete and tile roofs. Roofs in areas with high rainfall and high humidity are most susceptible to moss growth. However, roofs all over the country are plagued with moss problems. Fortunately, there is a way to remove moss from your roof and prevent it from returning.
Mosses are flowerless and seedless plants that can be found growing on rooftops, decks, lawns, walkways and other outdoor surfaces. Mosses grow best in wet and shady areas. There are thousands of species of moss. Species of moss commonly found on rooftops include Dicranoweisia cirrata, Racomitrium canescens, Antitrichia californica, Scleropodium cespitans and Bryum argenteum.
Moss itself does not cause much damage to roofs. However, moss collects water, which does accelerate wear and tear on roofing materials and can lead to leaks. Moreover, many people find moss unsightly, and, over time, moss can discolour a roof.
To remove moss from a roof, attach a standard bristle scrub brush to a pole and push the brush down the roof to tear the moss's shallow roots from the shingles. Avoid pushing the brush up the roof, as this may loosen or break the bond between the shingle layers. Use a power washer to remove any loose pieces of moss. Note that while some people recommend using chlorine bleach to remove moss, this may discolour the roof. Moreover, chlorine bleach runoff may kill vegetation on the ground and accelerate corrosion of metal gutters. Be careful when removing moss from a roof. Moss can be slippery, especially when wet. Wear shoes with good traction and sit, instead of standing, whenever possible.
To prevent moss from returning, place copper strips, available at roofing stores, near the top of the roof. Slide one edge beneath a row of shingles but be sure to leave at least 4 inches of copper exposed. When it rains, the rain will wash copper molecules down the roof. This creates a poisonous environment for both moss and algae. Zinc may be an effective alternative to copper, but copper is generally considered more effective and longer lasting.