Black mould in bathroom in Santa Coloma de Gramenet: causes, cleaning and lasting fix
Resumen rápido
Bathroom mould is usually condensation, not a leak.
¿Qué está pasando?
Shower steam pushes humidity above 80%.
Causas más probables
Poor ventilation after showering
altaSmall fan or blocked duct.
Failing silicone seals
altaAfter 3-5 years it loses its biocide.
Thermal bridge on outer wall
mediaBuildings without insulation have cold corners.
Pasos de diagnóstico
- 1
Clean with diluted bleach
Spray, wait, scrub.
⚠ Parada de seguridad: Never mix bleach with ammonia. - 2
Replace blackened silicone
Cut out and apply sanitary silicone.
- 3
Improve post-shower ventilation
Run the fan 15-20 min after.
Cuándo llamar a un profesional
Call if it returns in 2-3 weeks or exceeds 1 m².
Coste orientativo en Santa Coloma de Gramenet
80–280 €
Silicone replacement and antimould primer.
Contexto local · Santa Coloma de Gramenet
Santa Coloma de Gramenet's climate has high humidity year-round.
Santa Coloma de Gramenet is almost entirely 1960s–70s buildings put up for internal migration, with 8–14-storey blocks in Singuerlín, Riu Nord and Llatí. That vintage explains what we see most: carbonation damp on garage ceilings, aluminium wiring that needs checking before any work, and fibre-cement stacks that need a special protocol to touch. In bathroom refurbs we routinely uncover tiling stuck straight to mortar with no membrane, which forces us to chase further than expected. The slope toward the Besòs limits van access on some central streets.
- Comarca: Barcelonès
- Población: 121.278 hab.
- Parque de vivienda predominante: piso-moderno
- Año medio de construcción: 1974
- Códigos postales: 08921, 08922, 08923, 08924
Ciudad densa al norte del Besòs, con torres de viviendas de los 70 y vivienda obrera en Singuerlín y Fondo.
Preguntas frecuentes
Is bathroom mould a health risk?
For asthmatics and young children, yes.
Does bleach kill mould completely?
Surface only — if it penetrated it returns.
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Más sobre Damp, mould and paint
Sources and regulation
- CTE DB-HS 1 — Protección frente a la humedad — Código Técnico de la Edificación