What Causes Mould in the Home?
Mould in the home is common, and in almost every case it's treatable once you understand what's causing it. This guide walks through the main causes so you know what you're dealing with — and what to do next.
The three usual causes
Most household mould comes down to one of three sources of excess moisture. They often overlap, which is why a proper inspection matters.
- Condensation — warm, moist air meeting a cold surface, most often on windows, cold walls and in bathrooms.
- Penetrating damp — water getting in from outside, through a damaged roof, wall or window seal.
- Rising damp — groundwater moving up through a wall, usually where a damp-proof course has failed or is missing.
Condensation is the most common
Everyday activities like cooking, showering and drying clothes indoors all add moisture to the air. Without enough ventilation, that moisture settles on cold surfaces and, over time, mould can take hold — especially in poorly ventilated bathrooms and kitchens.
Small changes that help
- Keep trickle vents open and use extractor fans when cooking or showering
- Wipe down windows and sills if condensation builds up overnight
- Allow a little space between furniture and external walls for airflow
If mould keeps coming back despite good ventilation, that's usually a sign something else is going on — it's worth getting it looked at rather than treating the surface mould alone.
When to get help
If you're a social housing tenant, your landlord has legal timeframes to investigate and fix significant damp and mould hazards. For everyone else, a professional survey is the fastest way to a clear answer — see our damp survey service for details.