Steel roofing can sometimes develop issues when algae and moss grow on its surface. These growths primarily appear in damp, shaded areas of the roof where moisture lingers, providing an ideal environment for spores to settle and multiply. Algae often show as dark streaks, while moss is the fuzzy green covering that may trap moisture against the steel, potentially leading to corrosion over time if untreated. Steel itself is durable but requires proper maintenance to keep these growths from causing damage. Simple diagnostics can be done by visually inspecting the roof after rain or during humid conditions, focusing on north-facing slopes or shaded spots where sunlight is limited. You can safely check for algae or moss by gently touching the surface—moss will feel soft and thick, while algae may appear slimy or stained.
For a safe DIY solution, start by using a soft-bristle brush and a mild cleaner specifically designed for metal roofs, rinsing thoroughly with water to avoid harsh chemicals that could void the steel roof’s warranty. Avoid pressure washers, which can damage the metal coating. If the algae or moss covers large areas or the steel shows signs of rust beneath, it’s time to call a professional roofer. When consulting a contractor, ask how they would safely remove the growth without harming the roof’s protective layers and what preventative treatments they recommend. Also, inquire whether their methods or materials might affect your roof’s warranty, ensuring any fixes done maintain the steel roofing’s longevity and performance.