On Thu, 07 Dec 2006 17:26:45 -0600, "MiddleO"
wrotF:

My roof (only 6 years old) has black streaks running down it. What is
causing these? My previous roof had the same stains, and I had the roof
replaced. These are supposed to be 20yr shingles.

Does anyone know what is going on?



Middle Ohio homeowner

Algae probably, but possibly tannin from clumps of leaves that collect
on the roof and then the rain water dissolves the tannin and it
streaks down. You see that same effect on concrete sidewalks in the
fall after leaves have been rained on and then blown away.