Why are there streaks or stains on my roof?
Dark streaks or stains usually show up first and most often on the north-facing slope of the roof which gets less direct sunlight. These streaks or stains are usually caused by algae growth that can be prominent on areas of the roof the get the least amount of sun. They will not affect the longevity of the roof or its waterproofing capabilities. Zinc strips or various cleaners can be used but they are temporary solutions. Be cautious when cleaning because harsh cleaners or pressure washers can damage the roof system and result in granule loss.