Is black mould on walls dangerous, and what should I do?

The honest health picture

Black mould is not just unsightly — it can be a real health risk, and we won’t downplay it. Damp and mould release spores and tiny particles that, breathed in over time, can trigger or worsen coughing, wheezing, allergic reactions and asthma. For most healthy adults a small amount is a nuisance; the serious risk is to more vulnerable people.

We also won’t overstate it: a single small patch you clean promptly is not a crisis. The danger comes from prolonged exposure to significant, recurring mould — which is exactly what happens when an underlying damp problem is left unfixed.

Who is most at risk

• Babies and young children — among the most vulnerable.
• Elderly people.
• Anyone with asthma, COPD or another respiratory condition.
• People with weakened immune systems.

This is the human reason the law changed. Awaab Ishak, a two-year-old, died in 2020 after prolonged exposure to mould in his home — and a coroner found the mould directly contributed. If you have a baby, a child, or a vulnerable adult in a mouldy home, treat it as a priority, not something to live with.

How to clean a small patch safely

For a small area (roughly under a square metre) you can deal with yourself:

1. Ventilate the room — open a window.
2. Protect yourself — wear gloves, and ideally a mask, and consider eye protection.
3. Wipe, don’t dry-brush. Use a proper mould remover or a suitable cleaning solution and wipe the mould away. Dry-brushing or hoovering flicks spores into the air.
4. Bin the cloths afterwards; don’t reuse them.
5. Dry the area and keep the room ventilated.

Do not tackle large areas yourself, and don’t disturb extensive mould if anyone in the home is vulnerable — get professional help.

Cleaning is not the cure

Here’s the key thing: wiping mould off only removes the symptom. If it keeps coming back, there’s an ongoing damp problem feeding it — usually condensation on cold walls, a leak, or penetrating damp. Until that’s fixed, you’ll be cleaning forever.

And removing that underlying damp, where it’s caused by the building’s condition, is your landlord’s responsibility, not yours. (See is my landlord responsible for condensation and mould?)

What to do about recurring mould

1. Clean the visible patch safely, as above.
2. Improve ventilation where you can — fans, trickle vents, wiping condensation, leaving gaps behind furniture on cold walls.
3. Report it to your landlord in writing, describing the mould, where it is, and any health effects — especially for children or vulnerable people. Our reporting guide and template makes this quick.
4. Escalate to Croydon Council’s environmental health team if the landlord doesn’t act — serious mould affecting a vulnerable person is exactly what they can step in on.

A Croydon note

In Croydon’s cold-walled terraces and converted flats, recurring black mould in the same corners every winter is the classic sign of a condensation problem driven by the building — cold surfaces plus weak ventilation. That’s a fixable building issue, and it’s the landlord’s job to fix it. If that’s your home, you’re not imagining it and you’re not the problem.