By Barry Stone
Dear Barry,
My gray shingle roof is about 10 years old and is gradually turning green, kind of like there's a fungus on it. What can I do to clean it and prevent worse damage? - Judy
Dear Judy,
Roof surfaces that receive little or no sun exposure are prone to grow a thin layer of algae. This commonly occurs on northern exposures or where roofs are shaded by tall trees. Typically, algae does not adversely affect the condition of the shingles, therefore, removing it is not essential to maintaining the integrity of the roof. However, if restoring the original color of the shingles is desired for cosmetic reasons, you can try washing the roof with a watered down solution of algaecide, such as would be used for swimming pools. But no guarantee of satisfactory results can be made without first inspecting the roof.
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