This can be a couple of things…it can be moss, Black mold, mildew or a lichen. This can all cause a lot of damage in the long run but also has instant bad effects like causing bad allergies or making allergy season harder on yourself or family members. These molds will grow over time and eventually take over your roof. A lot of homeowners get very worried because they initially think that they need a new roof but in fact this can just be treated the right way and can eradicate the issue. Power washing or pressure washing is never the solution here, those methods can cause major damage to the roof avoid these solutions at all cost. Give us a call and we can explain the correct cleaning process today.