Kelly Roofing is often asked, “What is the best way to clean our roof?” Here in Florida we tend to have aggressive algae build-up. Here are our findings: Do not use Chlorine or Sodium Hydroxide: These chemicals are not only harmful to the asphalt membranes and materials that comprise the main waterproofing layer, but more importantly, these chemicals corrode the metal flashings and fasteners. Flashings bridge transition areas and fasteners hold the system together. Additionally, using these types of chemicals will void your roof’s warranty and potentially cause damages to other parts of the building and surrounding foliage. There are natural products available, which provide a cleaning solution without the harmful side effects.