A common sight in wet winter climates is bright green moss growing on the roofs of both expensive and inexpensive homes. Here in Portland, Ore., thick moss on shingled roofs is particularly common. While roof moss may seem to be just a cosmetic problem, if left in place, it can severely damage your roof and even have disastrous consequences for other parts of your home.Moss is a plant that grows naturally on just about any surface, including the ground, trees, and sidewalks, as well as roofs. It produces tiny spores that become airborne and land on roofs and other prospective...

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