Lichen

Lichen differs from moss in several important ways. While moss is a simple plant that grows on top of the roof surface and can be relatively easily removed, lichen forms a tight bond with the substrate through chemical and physical means. The fungal component of lichen produces acids that slowly dissolve the mineral surface of tiles, creating a micro-textured bonding surface that makes removal very difficult without high-pressure cleaning. Lichen appears as flat, crusty patches in various colours — grey-green, orange, black, and white are common. Lichen is remarkably resilient. It can survive extreme drought by entering a dormant state, resuming growth when moisture returns. It is also resistant to most chemical treatments, as the tough outer cortex of the lichen body protects the living cells within. For these reasons, lichen on roofs is best addressed by high-pressure cleaning at 3,000-4,000 PSI, which physically removes the organism and its attachment structures from the tile surface. In Gippsland, lichen is commonly found on older concrete tile roofs, particularly in rural areas with clean air and minimal pollution (lichen is actually an indicator of good air quality). While lichen itself does not cause structural damage, it is unsightly, increases surface roughness (promoting further biological colonisation), and etches the tile surface. Town & Country Roofing removes lichen during the pressure-cleaning stage of restoration, and the subsequent membrane coating creates a smooth, sealed surface that resists lichen recolonisation.