What Causes the stains or streaks on asphalt roof shingles?
The discoloration on roofs seems to be an ever increasing problem. It has been referred to in the roofing trade as “Fungus Growth” or “Mildew”. but is actually algae growth. Algae usually appears as a brown-gray to black appearance and may be confused with dirt or soot build up. It is less likely to be noticed on black or darker colored roofs. There are several types of roof algae.
