What causes roof stains?

Does your roof have dark stains all over the shingles?  If you look around you can see these stains on almost every roof.  Primarily in humid climate parts of the country.  The dark stains are a form of algae that grows on the north side of the roof where it gets less sunlight.  Asphalt shingles have limestone added as a filler and the algae growing on the roof feeds on the lime stone.  As time goes on the algae gets worse and continues to grow slowly pre-maturing the life of the shingles.  Proper cleaning will remove the stains and eliminate the algae spores.  Visit http://www.cleantheroof.com to see pictures and video showcasing our work.  M&D Power Washing out of Fort Wayne, Indiana serving all of Allen county.  Give us a call 260-413-3290 Fort Wayne, Indiana