Green algae or mildew on siding — Chicago, Illinois
Green or black streaks on vinyl, wood, or fiber-cement siding are usually algae (Gloeocapsa magma) or mildew colonies fed by moisture and shade. Left alone they trap moisture against the surface, accelerating rot in wood and degrading paint. A professional pressure washing ($200–$500 for an average home exterior) removes these growths in 2–3 hours using a soft-wash technique — low pressure (under 1,500 PSI) with a sodium hypochlorite or oxygen bleach solution that kills spores without damaging siding. Standard high-pressure washing can force water behind siding laps on vinyl and splinter softwood grain, so soft-wash is the industry standard for building exteriors.
Who to call
For this problem in Chicago, call a: Schoonmaker
Vind een Schoonmaker in ChicagoSymptoms to look for
- Green, black, or dark streaks on siding that don't wash off with a garden hose
- Siding feels slimy or slippery to the touch in shaded areas
- Discoloration worsens on north-facing walls or under trees
- Musty outdoor smell near the house foundation
Spoeddienst in Chicago
Emergency home services in Chicago are widely available 24/7, with typical response times of 30–60 minutes. After-hours rates range from $100–$200/hour. During polar vortex events, heating emergencies can see delays of 4–8 hours due to overwhelming demand. Illinois requires plumbing and electrical licenses for all work.