Will moss grow on a metal roof?
Short answer. Moss rarely grows on the smooth face of a metal roof because there is little texture to hold spores or moisture, and water sheds quickly. It can still take hold where debris collects, such as behind chimneys, along lap seams and panel ribs, in valleys and on heavily shaded north slopes, and algae or mildew can stain painted metal.
Where it does show up
- Debris traps. Behind chimneys and skylights and in valleys, leaves and needles pile up, hold water and break down into a thin soil moss can root in.
- Lap seams and ribs. On exposed fastener panels, side laps and ribs collect grit and stay damp.
- Shaded north slopes. Heavy tree cover on North Georgia mountain lots keeps metal wet for long stretches.
- Older, chalky paint. A weathered finish has more texture than new paint.
Why it matters on metal
Moss and wet debris hold moisture against the metal and the fasteners. That breaks down paint, starts corrosion at cut edges and screws, and dams water at seams. It also clogs the gutters below.
How to remove it safely
- Clear debris with a soft brush or leaf blower from a safe position. Wet panels are slick, so do not walk them.
- Use a cleaner the panel or paint maker approves. Harsh chemicals, wire brushes and high pressure can damage the finish and its warranty.
- Rinse thoroughly from the top down.
- Skip copper strips on steel or aluminum roofs, since mixing metals causes galvanic corrosion. Ask the panel maker before adding any metal strip.
Prevention
Trim overhanging limbs, keep valleys clear, and add a cricket behind wide chimneys so debris cannot pile up. See moss and lichen on roofs and metal roofing in Georgia.