Black mould in your home: what causes it and how to stop it for good

Black mould on walls and ceilings is the most visible sign of condensation, the most common form of dampness in any home, whatever its age. It brings a musty odour and can give rise to respiratory health problems, which is why it is worth fixing properly rather than wiping down every few weeks.

Why it keeps coming back

Mould grows where water vapour meets a cold surface. The vapour usually comes from kitchens, bathrooms and drying laundry, then travels through the home and condenses on the coldest walls, often in bedrooms or behind furniture where air does not move. Bleach kills the surface growth, but as long as the moisture and the cold spot remain, the mould returns.

The permanent fix

The remedy depends on the scale of the problem, and that is what a survey establishes. It ranges from improved ventilation and a proper fungicidal treatment, through insulation improvements that warm up cold surfaces, up to a heat-recovery ventilation unit for persistent cases. That is a quiet unit that continuously swaps stale, moist air for fresh, filtered air without losing heat.

What it almost never needs is a damp-proof course. Rising damp carries salts that hold mould back, so mould is not a sign of rising damp, and anyone specifying an injected DPC for a mould problem is fixing the wrong thing.