Lichen vs. Algae on Arizona Tile Roofs
Homeowners often mistake lichen for algae on Arizona tile roofs — both are biological growth, but lichen is significantly more damaging. Algae forms a surface film; lichen is a symbiotic organism (algae + fungus) that develops root-like structures called holdfasts that physically penetrate the tile surface, compromising integrity over time. Arizona's UV and temperature extremes accelerate this damage once lichen is established.
Lichen appears as circular grey, green, or orange patches — hard, crusty, and bonded to the tile surface. Unlike algae streaking (which runs downward from debris points), lichen grows in discrete circular patches wherever moisture conditions are favorable. North-facing roof sections and areas under tree canopy are most susceptible in Arizona.
Professional Lichen Removal from Arizona Tile Roofs
Lichen removal requires soft washing — biodegradable biocide chemistry applied at low pressure to kill the organism before any attempt at mechanical removal. Attempting to scrub or pressure wash lichen while alive risks tearing holdfasts through the tile surface, leaving microscopic damage channels. Professional protocol: biocide application, 15–30 minute dwell time to kill the organism, low-pressure rinse. Post-treatment algaecide inhibits regrowth.
Dead lichen releases from tile surfaces over 30–90 days after treatment as holdfasts die and the organism desiccates. For immediate visual removal, light soft-bristle agitation after biocide dwell time removes loosened material. Manufacturer warranty compliance requires soft washing only — high-pressure washing voids most Arizona tile roof warranties.