Dirty Roofs are caused mainly by algae and mold spores in the air finding a suitable environment to live on your roof. The dark streaks form as these spores multiply and work their way down the slope of roof. In our area the north side is always worse due to a lack of sunlight causing a damp place for the spores to grow. Our roof cleaning is done by coating the roof in a solution which kills everything living on the roof and leaves it looking like new. We take every precaution when cleaning the roof to protect everything else living below. All downspouts are bagged or have buckets placed under them to catch any extra runoff that may occur. We also rinse all surrounding grass and plants prior to the cleaning and after the cleaning to ensure nothing else is harmed other than the mold and algae on your roof. We clean all roof types with the same process and great results.