The first cold mornings of the year have a habit of showing you where the problems are. You open the bedroom curtains and the window is running with water. There’s a grey line of mould along the frame that wasn’t there in July. Condensation and mould turn up together, so getting rid of mould only works if you also stop condensation on the windows that feeds it.
You’re not the only one. A survey Uswitch ran with 3,000 UK residents in early 2026 found that 64% of households deal with condensation, damp or mould. Plenty of them said it got worse because they kept the heating down to save money. In London, where a lot of us live in older conversions or small flats with not much airflow, it tends to show up early.
Here’s how to get rid of mould properly, how to cut down the condensation that feeds it, and when to stop scrubbing and get help.
Why condensation and mould show up in London homes in autumn
Mould needs moisture, and condensation gives it plenty. Warm, wet air from showers, cooking, kettles, drying laundry and simply breathing hits a cold surface (a window, an outside wall, the back of a wardrobe) and turns into water. Do that every day for a few weeks and you get the black spots.
Autumn is when this starts because the outside temperature drops, windows stay shut, and washing moves indoors, so condensation on the glass builds up every night. The clocks go back on Sunday 25 October 2026. After that the evenings get dark early and most people stop opening windows at all.
The Uswitch research also shows where it usually turns up:
- bathrooms (58% of people who had mould)
- bedrooms (49%)
- window sills (41%)
- ceilings (27%)
- behind furniture (26%)
That last one catches people out. A wardrobe pushed flat against an outside wall creates a cold, still pocket of air, and you won’t see the mould until you move the furniture.
How to get rid of black mould on walls, windows and sills
Small patches of surface mould (roughly the size of a hand towel or smaller) are usually safe to remove yourself. Anything bigger, or mould that keeps coming back in the same place within a couple of weeks, points to a damp problem, and you won’t get rid of mould like that with cleaning alone.
UK government guidance on the health risks of damp and mould lists who is most at risk: people with asthma or other lung conditions, anyone with a weakened immune system, children, older people and anyone who’s pregnant. If that’s you or someone you live with, ask someone else to clean mould for you.
What you need
- rubber gloves, goggles and a mask that covers your nose and mouth
- a bucket of warm water with a bit of washing-up liquid, or a mould and mildew cleaner made for the surface you’re cleaning
- a soft cloth or sponge, and a dry cloth
- a plastic bag for the used cloths
Step by step
- Open the window and close the door to the rest of the flat, so spores don’t drift into other rooms.
- Take soft furnishings out of the way. Clothes, curtains and bedding that have mould on them need a hot wash, not a wipe.
- Wipe, don’t brush. Dry brushing throws spores into the air. The safest way to remove mould is to wipe it off gently with the damp cloth, rinsing it often.
- Dry the surface completely with a clean cloth. Leaving it damp is how mould comes straight back.
- Bag the cloths and throw them away, or wash them on a hot cycle straight away.
- Vacuum and wipe the room afterwards to pick up anything that settled.
A word about bleach. Government guidance recommends a proper mould and mildew cleaner instead, and there’s a good reason. Bleach will make black mould look lighter on hard, shiny surfaces like tiles, but on painted plaster or wood it often just bleaches the colour and leaves the growth underneath. And never mix bleach with other cleaning products. Bleach and anything acidic or ammonia-based can release gases you really don’t want to breathe in a small bathroom.
Black mould on silicone and window seals
Black mould on shower sealant is one of the most searched cleaning problems in the UK every autumn, and you can’t always get rid of mould once it has grown into the silicone itself. Surface cleaning only goes so far there. If the sealant is still black after a proper clean, the fix is to cut it out and reseal. It’s a cheap job and it makes a bathroom look years newer.
Window seals and the rubber gaskets around double glazing are similar. Clean them gently, dry them, and keep the drainage holes at the bottom of the frame clear so water can actually escape.
How to stop condensation on windows (and the mould that follows)
Cleaning will remove mould that’s already there, but condensation is what brings it back. If you want to stop condensation on windows for good, it comes down to moisture and air. None of it is complicated. It only works if you do it every day.
Wipe the windows every morning. Clearing the condensation on the glass takes a minute with a squeegee or a microfibre cloth. Wring it into the sink, not back onto the sill.
Ventilate while you’re making moisture. Extractor fan on during the shower and for 15 to 20 minutes after. Lids on pans. Fan on when you cook. If your extractor fan barely moves a piece of tissue, the filter is probably clogged or the fan needs replacing. A working fan will reduce condensation in a bathroom more than anything else.
Open a window a little, even when it’s cold. Ten minutes in the morning swaps wet air for dry air, and it’s one of the easiest ways to reduce condensation. If you have trickle vents at the top of your windows, leave them open. They’re there to stop condensation on windows, and most people keep them shut.
Keep the heating low and steady rather than blasting it for an hour and switching it off. Cold walls are what turn vapour into water, so a steady background temperature does more to prevent condensation than short bursts of heat.
Leave a gap behind furniture. Five to ten centimetres between furniture and any outside wall lets air move.
Close internal doors when you’re showering or cooking, so the steam doesn’t spread to cooler rooms like the bedroom, where window condensation is usually worst.
Drying clothes indoors without getting mould
In the Uswitch survey, 39% of people said they’re drying more clothes indoors than before. In a one-bed flat with no garden, it’s often the only choice. One load of wet washing can release a couple of litres of water into the air as it dries. That’s condensation and mould waiting to happen, so where you put it matters.
- Dry it in the bathroom with the door shut and the extractor fan on, or near an open window.
- Don’t hang clothes directly on radiators in bedrooms.
- Give it an extra spin in the washing machine so it goes on the airer as dry as possible.
- A dehumidifier next to the airer helps a lot, and it will also stop condensation on windows in that room. It pulls water out of the air and the clothes dry faster too. Aim for indoor humidity of roughly 40 to 60%. A cheap hygrometer will tell you where you are, and keeping it in that range helps prevent condensation on the windows too.
Damp and mould in a rented flat: who deals with it?
This is a question a lot of London tenants are asking right now, partly because of Awaab’s Law. It came into force for social housing on 27 October 2025 and sets strict deadlines for landlords to investigate and fix damp and mould. The Renters’ Rights Act gives the government the power to extend it to private renting, but as of autumn 2026 there’s no confirmed date for that yet.
That doesn’t mean private tenants have no protection. Under the Homes (Fitness for Human Habitation) Act 2018, a private landlord in England has to keep the property free of serious hazards, and serious damp and mould counts. As a general rule:
- Condensation mould caused by day-to-day living is usually something the tenant is expected to manage by cleaning and taking steps to reduce condensation.
- Damp caused by the building (a leaking gutter, broken extractor fan, rising damp, a leak from upstairs, missing insulation) is the landlord’s job to fix.
If mould keeps coming back after you’ve cleaned and ventilated properly, report it to your landlord or agent in writing, with dated photos. Keep a record. It helps if there’s a disagreement later, and it matters for your deposit when you move out. Our guide on getting your full deposit back in London covers that side of things.
One thing that often gets missed is the outside of the building. Blocked gutters overflow down the walls and soak into brickwork, and that shows up as damp patches on the inside a few weeks later. If you own a house, getting the gutters cleared before the heavy rain in October and November is one of the cheapest ways to protect your walls.
When to call in a professional clean
Sometimes the problem is simply that there’s too much to catch up on. The bathroom grout has gone grey, the window frames in every room have that dark line, and the extractor fan hasn’t been cleaned since you moved in. That’s where a deep clean earns its money, because it gets rid of mould in all the places you’ve been putting off.
A good autumn deep clean should cover:
- tiles, grout and sealant in the bathroom and kitchen
- window frames, sills, seals and tracks, inside
- extractor fan covers and cooker hood filters
- skirting boards and the wall behind furniture
- the inside of wardrobes against outside walls
At CityHousekeeping, our cleaners bring their own products and equipment, and you can add specific areas when you book. If you only want the bathroom and windows done properly before winter, a one-off deep clean is usually the right fit. For the windows themselves, inside and out, have a look at our window cleaning service.
A deep clean will remove mould from surfaces, but it won’t fix structural damp, and we’ll tell you if we think that’s what’s going on. What it does is give you a clean starting point. After that, the daily habits above are what stop condensation on windows and keep mould away.
After that, regular cleaning every week or fortnight stops the build-up from starting again. If you’re not sure how often you need a deeper clean, we’ve written about how often to book a deep clean in London. And for the rest of the house, our autumn cleaning guide goes room by room.
Questions we get asked a lot
How do I get rid of black mould permanently?
To get rid of mould for good, clean it off, dry the surface completely, and then deal with the condensation that caused it. Without better ventilation, lower humidity and steady heating, mould usually comes back within a few weeks. If it returns in the same spot quickly, there may be a leak or damp problem that needs a landlord or a damp specialist.
Why do my windows have condensation on the inside every morning?
Warm, moist air from breathing, showering and cooking hits the cold glass overnight and turns to water. Left alone, that condensation is what feeds mould on the frames. It’s most common in bedrooms with the door shut. To stop condensation on windows, wipe the glass each morning, open the trickle vents, and run a dehumidifier in that room.
Is it safe to clean mould myself?
For small patches, yes, if you wear gloves, goggles and a mask and keep the window open. UK government guidance says people with asthma, lung conditions or weak immune systems are most at risk, and larger areas of mould should be dealt with by professionals.
Does bleach kill black mould?
It can help clean mould off hard, non-porous surfaces like tiles. On painted walls, wood or plaster it often just lightens the colour and leaves the growth underneath. Never mix bleach with other cleaning products.
Is my landlord responsible for damp and mould in my flat?
If the mould is caused by a problem with the building, like a leak, broken ventilation or rising damp, the landlord is responsible for fixing it. Condensation from daily living is usually for the tenant to manage. Awaab’s Law currently applies to social housing only, not private rentals.
Can a cleaning company remove mould?
Yes. A professional deep clean can remove surface mould from tiles, grout, window frames and sills. It won’t fix the cause if the damp comes from the structure of the building, and mould that has grown into sealant usually needs resealing.
Want to get rid of mould in the bathroom, windows and hidden corners before winter? Book a deep clean online or get in touch and tell us what you’re dealing with.
