Black Algae & Mildew on Siding — Myrtle Beach Homes
Black Algae & Mildew on Siding — Myrtle Beach Homes — what this page covers
What looks like dirt on Myrtle Beach siding is usually a living colony of algae and mildew. High-pressure blasting removes the visible streaks but leaves the roots — the film returns in 6–10 weeks. A soft wash with sodium-hypochlorite and surfactants kills the organism, and the siding stays clean 12–18 months.
Signs you have this problem
Green or black vertical streaks on the north and east faces of homes
Looks worse after rain — the film is alive and feeding on humidity
Common on vinyl and HardiePlank in shaded, tree-lined Horry County lots
Left alone it stains and can etch paint over multiple seasons