Why Exterior Walls Develop Black Stains: Causes and Fixes
Exterior walls develop black stains when moisture allows biological growth, airborne soot and dust to adhere, or metals and minerals to oxidize and migrate through the facade. The most common causes are algae or cyanobacteria on slow-drying surfaces, fungal growth near persistent leaks, pollution film, and dirty roof or gutter runoff. Correct identification must come […]