When people find mould, the first assumption is a leak. But in a lot of homes — especially well-sealed modern ones — the water is coming out of the air, not a pipe. That’s condensation, and it’s a common, easily-missed cause.
How it happens
Warm, humid indoor air hits a cold surface — a window, an external wall, the inside of a wardrobe on a south wall — and the moisture condenses out. Do that day after day and you’ve got a damp surface that grows mould, with no leak in sight.
Fixing it
Condensation mould is a ventilation and airflow problem. Exhaust fans that vent outside, better airflow, managing indoor humidity and sometimes addressing cold spots in the building fabric are what break the cycle. Cleaning the mould without fixing the condensation just resets the clock.
If your mould keeps coming back in the same cold corners with no leak to find, condensation is the prime suspect.
Related infographicWhy mould is still coming backGeneral information only — every property is different, and nothing here replaces a professional, on-site assessment.
