Black streaks or black roof stains on asphalt shingles are caused by a hardy type of airborne algae. This algae is simply known as roof algae. It usually first appears on the north facing slopes where moisture and shade are most prevalent.

The algae lands on your roof and feeds on the nutrients in the shingles. As it rains the algae is spread down the roof causing unsightly black stains. It is a fact that 50% of the roofs that are replaced in the Midwest are replaced due to appearance and not functionality. Replacing a roof that only needs cleaned is like replacing vinyl siding because it develops mildew, it doesn’t make much sense.

Some roofing contractors may not provide you with accurate information. Some won’t be honest because obviously they want to replace your roof, others are simply uneducated about cleaning shingles. Some roofing contractors think that black streaks are a sign of wear. Or they may tell you that roof cleaning will damage your shingles.

It is true that using too much pressure on your shingles can do more harm than good, you should never allow a pressure washer to be used on your roof. With that said, the major shingle manufacturers do recommend cleaning shingles using low pressure methods so no damage is done. They also have suggested roof cleaners and roof cleaning chemicals that should be used.

Not taking care of a roof suffering from roof algae will result in the algae taking over the entire roof. This algae will diminish the life of your roof, will increase your home cooling costs, and depletes your homes perceived value. Low pressure roof cleaning can save you thousands of dollars over a premature complete roof replacement. You may not get the whole truth by calling a roofing contractor, so first educate yourself and consider calling a roof cleaning company to come out and discuss your problem with you.