UK mould treatment guide
Black mould on walls, ceilings and silicone is treatable. But treating the surface without fixing the humidity that caused it means it will be back. Here is how to do both — safely and effectively.
UK guide
Anti-mould spray kills surface mould in minutes. A dehumidifier stops it returning. Both are needed for a lasting fix.
Before you buy any products, check whether the mould is something you can handle yourself or whether you need a professional.
Anti-mould spray and bleach both release fumes that can irritate your lungs, eyes and skin. Work safely:
Follow this process carefully to avoid spreading spores to other surfaces:
Bathroom silicone sealant is porous and mould roots embed deeply — bleach often fails here because it cannot reach the root system. The most effective approach:
Condensation on windows runs down the glass and collects on wooden or uPVC frames — mould feeds on the organic material in frame sealants and paints.
The highest-humidity room in most UK homes. Steam from showers creates ideal conditions. Key actions: use the extractor fan during and for 15 minutes after every shower. Replace any broken or ineffective fan. Treat shower cubicle silicone every 6–12 months. Keep the bathroom door closed when showering to prevent humidity spreading to the hallway and bedrooms.
Bedroom mould is often caused by condensation from poor ventilation or an en-suite bathroom with steam entering the bedroom. People spend 8 hours a night breathing the air in here — mould and high humidity affect sleep quality and respiratory health. Key actions: run a dehumidifier in the bedroom, especially in winter. Open windows for 10 minutes each morning. Check that en-suite bathroom extractor fans are working and venting correctly.
Cooking steam, boiling kettles and dishwashers all add moisture to kitchen air. Key actions: always use a lid on pans when cooking. Turn on the extractor fan or open a window when cooking. Wipe down kitchen surfaces and window sills each morning to remove condensation. If you have a Tumble Dryer, make sure it vents to the outside, not into the kitchen.
Single-glazed windows and poor insulation cause cold surfaces where condensation settles on walls and window frames. Key actions: open windows for 10 minutes twice a day even in winter. Use a hygrometer to check humidity — keep it below 60%. A dehumidifier run for 2–3 hours in the afternoon is usually enough for a typical living room.
This is the most important step. Mould is a symptom of excess humidity — treating the mould without fixing the humidity is like mopping a floor while the tap is still running.
Most mould treatment goes wrong because the right product is used on the wrong surface. Bleach brightens a porous material without killing what is underneath it, and abrasive scrubbing damages plaster so that mould returns more easily. Match the method to the material:
| Surface | What works | What to avoid |
|---|---|---|
| Tiles, glass, sealed vinyl paint | Mould spray or diluted bleach, left to dwell then wiped off | Leaving bleach sitting on grout - it attacks the cement |
| Painted plaster walls and ceilings | Dedicated mould treatment, dry fully, then a stain-blocking primer before repainting | Bleach alone - it fades the stain but the mould returns |
| Bare plaster | Treatment, thorough drying, then seal or paint | Painting over plaster that is still damp - it peels and mould returns |
| Bathroom silicone sealant | Cut out and replace the silicone | Any surface treatment - the mould is inside the sealant |
| Grout between tiles | Treatment, then a grout pen or re-grout if deeply affected | Hard scrubbing, which opens the grout up further |
| Curtains and soft furnishings | Wash at the highest temperature the fabric allows, then dry outside | Bleach, which destroys most fabrics |
| Wallpaper | Remove and dispose of it, then treat the plaster underneath | Trying to clean it - mould grows through the paper |
Whichever method you use, treatment is only half the job. Mould needs moisture, so if the room stays humid the growth is back within weeks. That is the part the dehumidifier size calculator and the running cost calculator help you plan for.
DIY treatment is appropriate for small, surface-level mould caused by condensation. Call a professional damp and mould specialist if:
Enter your room size and humidity level to find the right dehumidifier. Prevents under- or over-buying.
Work through 12 signs of damp, condensation and humidity problems in your home — room by room.
See how much it costs to run a dehumidifier in your home using 2026 UK electricity rates.