Green algae or mildew on siding — Barcelona, Catalonia
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 Barcelona, call a: Schoonmaker
Vind een Schoonmaker in BarcelonaSymptoms 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 Barcelona
Emergency services in Barcelona respond within 30–75 minutes in the central districts (faster in l'Eixample and Gràcia, slower in the upper hillside neighbourhoods). Callout rates run €60–€150 plus €45–€80/hour including IVA — among the highest in Spain alongside Madrid. Confirm the contractor is a registered instal·lador autoritzat with the Generalitat before granting entry, especially for heritage-building work.