Continued moss build up on roofs can cause the shingles to lift. This may cause costly leaks or intense water damage down walls and ceilings. In the Pacific Northwest it is more important than ever to inspect your roof every year,keeping valleys,  gutters and roofs free of debris. Composition,Tile  and Cedar roofs should be treated for moss every 3-5 years,depending on the location of the house. The more trees surrounding your house, the more maintenance. Yearly, maintenance can increase the life of your roof no matter what type 50-70%.  In the long run this will save you thousands of dollars in re roofing cost!

Edward J Baumann