Black mould removal
Black spots in the corner of the ceiling, round the window or along the bath sealant are the most common reason people look for help. Here's what a specialist will actually do about it.
We don't carry out the work. We're a free matching service that passes your enquiry to one independent damp and mould specialist near you.
Why black mould grows where it does
Mould needs a damp surface and a bit of time. In most Scottish homes the damp comes from the air inside, not from the walls. A family of four can put several litres of water into the air every day just from breathing, showers, cooking and drying washing. When that air reaches a cold surface it turns back into water, and the dark spotting follows.
That's why the same places get it again and again:
- the top corners of rooms on outside walls
- window reveals and the bottom of single-glazed or older double-glazed frames
- behind furniture standing against an outside wall
- bathroom ceilings with no extractor fan, or a fan that's too weak or switched off
- silicone and grout around baths and showers
- inside wardrobes and cupboards on a gable wall
If the mould is low down, alongside a tide mark, or near a downpipe, the cause may be water getting in from outside instead. That's a different fix, which is why the first job is finding out which it is.
What black mould removal involves
Treating the surfaces
Painted plaster and tiles can usually be cleaned with a fungicidal wash, left to work, and wiped down. Wallpaper with mould through it is normally stripped. Sealant is cut out and replaced. Mouldy carpet underlay or soft furnishings are often better thrown out than cleaned.
Checking what's underneath
Where mould has been there a long time, the plaster behind it can be damp right through. A specialist will usually test it with a meter. Damp plaster has to dry before anything is redecorated, and badly damaged plaster may need replacing.
Stopping it coming back
This is the part that's easy to leave out of a cheap quote. Depending on the cause, it might mean a better extractor fan in the bathroom, a continuous-running fan, trickle vents fitted to windows, insulating a cold ceiling void, or fixing a gutter. Our page on condensation and ventilation fixes goes into those options.
What you can do in the meantime
- Open the window or put the fan on when cooking and showering, and for a while after.
- Dry washing outside, or in one room with the door shut and the window open.
- Pull furniture a few centimetres away from outside walls.
- Wipe condensation off windows in the morning.
- Avoid bleach on porous surfaces: it can bleach the colour without dealing with the growth.
None of this replaces finding the cause, but it slows things down while you wait for a visit.
Costs
A small area of black mould in one room is at the cheaper end of the ranges in our cost guide, often around £150–200 for a single wall based on UK averages. Prices climb when plaster has to be replaced or several rooms are affected. These are typical ranges, not quotes; the specialist will price your job after seeing it.
Common questions
Is black mould a different thing from ordinary mould?
"Black mould" is a description, not a single species. Several common moulds grow dark grey, green or black on damp surfaces. A specialist treats them in much the same way, and the cause is what matters more than the colour.
Can black mould be removed from silicone sealant?
Not really. Once it's grown into the sealant around a bath or shower, the usual answer is to cut the old sealant out, treat the area, let it dry and reseal.
Why is it always in the bedroom corners?
Those corners are often the coldest part of the room, where two outside walls meet the ceiling. Moisture from breathing overnight condenses there first. Better heating, ventilation and sometimes insulation are the long-term answer.
Should I paint over it?
No. Painting over mould without treating it hides it for a short while and it usually shows through again. Anti-mould paint helps only after the surface has been properly cleaned and the cause dealt with.
Get a free quote
This is a free matching service, not the firm doing the work. We pass your details to one independent damp and mould specialist who covers your postcode. They contact you, arrange a visit and quote you directly. You don't pay us anything.