Advice · 4 min read · Updated 6 November 2026
10 mould myths busted: what really works in UK homes
Myth 1: bleach kills mould for good
Bleach is very good at removing colour, so a bleached patch looks clean. On non-porous surfaces such as glazed tiles and glass it can kill surface growth. On plaster, grout, silicone and timber, though, the mould grows into the material, and bleach is mostly water, which can soak in and feed what is left. That is a big reason mould reappears in the same spot within weeks. A fungicidal mould wash designed for walls, left on for the stated time, is more effective, and badly stained silicone usually needs replacing rather than cleaning.
Myth 2: vinegar and bicarbonate of soda are just as good
White vinegar can kill some common household moulds and is a reasonable option for a very small patch on a hard surface. It is slower and less reliable than a proper fungicide, and it does nothing about the cause. It also should never be mixed with bleach, because combining bleach with acids or ammonia-based products can release harmful gases. Bicarbonate of soda is a mild abrasive that helps scrub but is not a strong fungicide.
Myths 3 and 4: all black mould is toxic, and white mould is harmless
Many different moulds look black, green or grey. The species people call toxic black mould, Stachybotrys chartarum, usually needs material that has been soaking wet for a long time, such as after a leak. Most black spots on bathroom ceilings and window reveals are other common moulds. That does not make them safe: the UK Health Security Agency guidance is clear that damp and mould of any kind can affect breathing, allergies and asthma, and that some people are more vulnerable. Colour does not tell you how harmful a mould is, so treat any visible mould as something to clean and fix.
Myth 5: anti-mould paint solves the problem
Anti-mould paint contains a fungicide that slows regrowth on the painted surface, and it is a sensible finish after a proper clean. On its own it does not stop condensation, so mould can still grow on dust, soap residue or furniture nearby, and the fungicide becomes less effective over time. Painting over live mould without cleaning it first just traps it under a new layer.
Myths 6 to 9: quick fixes and blame
| Myth | The reality |
|---|---|
| Mould is caused by lifestyle, so it is the occupant's fault | Government guidance says it is unreasonable to blame damp and mould on lifestyle; building issues, ventilation and heating are usually root causes |
| A dehumidifier fixes everything | It reduces humidity but will not fix leaks, penetrating damp or broken fans |
| Opening windows in winter just wastes heat | Short bursts of ventilation remove moist air quickly with little heat loss |
| Mould only happens in old houses | New builds often get condensation in their first winters while they dry out |
Everyday habits do matter: drying washing indoors without ventilation, closing trickle vents and not using extractor fans all add moisture. But habits alone rarely explain persistent mould in a home with good ventilation, insulation and heating.
What actually works
- Find the moisture source first: condensation, a leak, penetrating damp or rising damp
- Clean with a fungicidal mould wash and leave it for the contact time on the label
- Replace mouldy silicone sealant rather than scrubbing it
- Remove and replace heavily affected soft materials such as carpet underlay or plasterboard after a leak
- Fix ventilation: working fans, open trickle vents, kitchen hoods that extract outside
- Keep rooms evenly heated
- Redecorate with anti-mould paint only once the surface is clean and dry
- Check again after six weeks and through the next winter
Myth 10: a home test kit tells you if mould is dangerous
Home mould test kits, usually petri dishes left open in a room, will grow mould almost anywhere, because mould spores are always present in normal air, indoors and outdoors. A positive result tells you very little. If you can see mould or smell damp, there is a moisture problem to fix. Laboratory sampling has a place in some large commercial or insurance cases, but for a typical home the money is better spent on finding and fixing the cause.
Similarly, a moisture meter reading on its own does not prove rising damp. Meters are calibrated for timber and can read high on walls with salts or foil-backed paper. Readings are useful, but they need interpreting alongside what is happening in the building.
Frequently asked questions
Does mould go away on its own in summer?
Mould usually stops spreading when walls warm up and humidity falls, so it can look dormant in summer. The stain and spores remain, and growth typically restarts once condensation returns in autumn. Summer is actually the best time to clean, treat and redecorate affected areas, while walls are dry and windows can be opened.
Can I just wipe mould off with a damp cloth?
Wiping with a damp cloth spreads spores and leaves the roots behind, so the mould usually comes back. For a small patch, wear gloves and eye protection, use a proper mould wash, follow the label contact time and dispose of the cloth afterwards. Larger areas, mould on soft materials or mould that keeps returning are better handled with the cause investigated.
Is it safe to sleep in a room with mould?
The UK Health Security Agency says damp and mould can affect anyone's health, and that children, older people and anyone with asthma, allergies, lung conditions or a weakened immune system are more at risk. A small patch is not usually an emergency, but it should be dealt with promptly. Anyone with symptoms they think are linked should speak to their GP.
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