How do I remove mould?
How to remove black mould from walls, sealant and ceilings, and how to stop it returning by fixing the moisture causing it.
- Difficulty
- beginner
- Time
- 45 min
- Read
- 3 min
- Safety
- caution
Short answer
Wipe the mould off with a dedicated mould remover or a 1:4 bleach-to-water solution, leave it 15 minutes, then wipe clean and dry the surface thoroughly. Removing it is the easy part — unless you reduce the moisture feeding it, it will grow back within weeks.
Mould is not a cleaning problem with a moisture side-effect; it is a moisture problem with a visible symptom. It needs three things to grow: a surface, something organic to eat (paint, dust, plaster, sealant), and persistent damp. You can only realistically remove the third. That is why the cleaning step below takes twenty minutes and the prevention step is the one that actually matters.
Safety
What you'll need
- Rubber gloves
- Mould remover spray, or household bleach
- Disposable cloths or kitchen roll
- Face mask (FFP2 or better) (optional)
- Stiff brush for sealant and grout (optional)
Step by step
- Open a window and put gloves on before you start.Disturbing mould releases spores. Ventilation matters more than speed here.
- Vacuum loose surface growth if you have a vacuum with a HEPA filter.Skip this if yours doesn't — a standard vacuum will blow spores back into the room.
- Spray the affected area with mould remover, or a solution of one part household bleach to four parts water.Wet it properly rather than misting it. Dry mould sheds spores; wet mould doesn't.
- Leave it for 15 minutes without scrubbing.The contact time is what kills the growth. Scrubbing immediately just moves it around.
- Wipe away with a disposable cloth, working from the outside of the patch inwards.Working inwards stops you smearing spores onto clean surface.
- Bin the cloths immediately — don't put them in the washing machine.You'd be transferring spores to the machine and everything washed in it afterwards.
- Dry the surface completely with a fan or a dry cloth.Any residual moisture is a fresh start for whatever survived.
- Find and fix the moisture source before the surface has a chance to get damp again.Usually condensation from cooking, showering or drying laundry indoors — see the condensation guide below.
Tips
- On silicone sealant, mould grows *into* the silicone rather than on it. If bleach doesn't shift it after two treatments, the sealant needs replacing — no cleaner will reach it.
- Anti-mould paint buys time on a wall that keeps getting damp, but it treats the symptom. Use it after fixing ventilation, not instead.
- A cheap hygrometer (under £10) tells you whether you have a real humidity problem. Keep indoor relative humidity below 60% and mould struggles to establish.
- Cold external walls behind furniture are a classic mould site — pulling a wardrobe 5cm off the wall to allow airflow often solves it permanently.
Common mistakes
- Painting over mould — It grows through emulsion within weeks and you've now sealed damp into the wall.
- Scrubbing dry mould — It sends spores airborne throughout the room. Always wet it first.
- Treating the mould but not the moisture — Guarantees it returns, usually in the same spot within a month.
- Mixing bleach with limescale remover or ammonia cleaners — Produces toxic chlorine or chloramine gas.
Questions people ask
Does white vinegar work on mould?
It works reasonably on non-porous surfaces like tiles and glass, and it's a sensible choice if you'd rather avoid bleach. It is less effective on porous surfaces such as plaster or grout, where growth extends below the surface.
Is black mould dangerous?
Common household mould can trigger or worsen respiratory symptoms, particularly for people with asthma or allergies. Extensive growth in a home is a health concern worth acting on, and if anyone in the household has breathing problems, get it assessed rather than treated DIY.
Why does mould keep coming back in the same corner?
That corner is colder than the rest of the wall, so moisture in the air condenses there first. It's usually an external corner, a spot behind furniture, or a cold bridge in the structure. Improve airflow to it and raise its surface temperature.