Moss, algae, and lichens can cause damage to your roof and many homeowners find that it also looks bad! If left untreated, moss can shave years off of the life of your roof. Moss tends to spread rapidly, especially with the climate of Vancouver, BC's Lower Mainland, and the Pacific Northwest in general. Root systems grow between, underneath, and into the surface of your roof's shingles and tiles, creating the potential to expose your roof, as well as trap water and excess heat. In addition, algae bacteria noticeably stains many roofs, leaving large, ugly dark streaks. As the bacteria seeks food, it will feast on limestone filler in the shingles. Lichens are another organism that will end up removing the protective layers of shingles and tiles. All of these can lead to an unattractive look and even an early roof replacement!