Mildew or mold on exterior paint — Chicago, Illinois
Dark green, gray, or black splotches on exterior-painted surfaces — siding, trim, soffits, and window frames — are usually mildew or mold growth on the paint film itself. Mildew thrives on north-facing walls, shaded areas, and surfaces near sprinklers or dense landscaping where moisture lingers. Unlike dirt, mildew is organic growth that feeds on the paint's binder and won't wash off with water alone. A bleach solution test confirms mildew: apply a few drops of household bleach (1:10 dilution) — if the spot lightens within 1–2 minutes, it's mildew; if not, it's dirt or staining. Professional pressure washing with mildewcide ($200–$600 for a typical home) removes existing growth, but repainting with mildew-resistant paint ($40–$60/gallon) is needed if the paint film is degraded. Prevention: trim vegetation 12–18 inches from walls, redirect sprinklers, ensure gutters don't overflow onto siding, and use paint with built-in mildewcide for shaded exposures.
Why this is common in Chicago
Chicago's temperature extremes and moisture cause paint to crack and peel faster than in milder climates. Lead paint is prevalent in pre-1978 homes, and the city's strict lead ordinance requires certified contractors for remediation in homes with young children.
Who to call
For this problem in Chicago, call a: Painter
Find a Painter in ChicagoSymptoms to look for
- Dark green, gray, or black splotches concentrated on north-facing or shaded walls
- Discoloration that spreads gradually over weeks or months (unlike splatter or staining)
- Spots lighten when dabbed with diluted bleach (the mildew test)
- Musty odor near affected exterior walls, especially after rain
- Paint underneath the mildew appears soft, chalky, or degraded when wiped
Emergency Service 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.