Get a Like-New Looking roof while pROTECTing YOUR wallet & home against these 3 common problems: Moss is usually the most damaging roof growth because it is heavier (which causes it to grow deeper into your roof to support its weight) and holds more water against your roof. This burrowing into and holding water against your roof increases damage to roofing shingles and channels water into the underside which causes rotting. Leaving moss in place can damage the roof and even have disastrous consequences when water within them freezes. Gloeocapsa magma (or Black Streets), is blackish algae that thrives on moisture when left unchecked, can damage shingles. Black streaks causes your roof to absorb more heat because its dark black stain reduces the heat your roof can reflect. Not cleaning Black Streaks increases your cooling costs and can lead to a far worse situation for your roof because Black Streaks (Gloeocapsa magma) can combine with fungus to produce Lichen a more damaging growth described next. Lichen is a combination of algae and fungus and usually has a light, mint-green color. It doesn’t trap as much water against the surface of the roof as moss, but it can be acidic and has strands that can penetrate into the shingles. Lichen’s danger lies in its ability to burrow through one shingle to the one below it. Just 1/8 of an inch more and it’s leaking into your home.