Lichen is an association involving a fungus and a photosynthetic partner, such as an alga. It can grow on exterior surfaces including some roofing and masonry.
What this means at your property
Growth on a shaded surface does not by itself establish a roof leak or structural damage. The surface beneath it, moisture exposure and material condition need separate evaluation. Aggressive removal can affect an otherwise serviceable finish.
Should I scrape growth off the roof?
Ask for a material-specific inspection and the manufacturer’s care guidance before treatment. Keep the assessment focused on drainage, surface condition and any actual damage instead of judging the need for replacement from growth alone.