How to Stop Damp and Condensation in a Rented Flat

Most damp in a flat is condensation, not a leak. Cooking, showering, drying laundry indoors and simply breathing release litres of water into the air each day. When that warm, moist air meets a cold surface such as a window, an outside wall or a cold corner, the water condenses out as droplets, and if it cannot dry it feeds black mould. True penetrating or rising damp exists but is far less common, and it is the landlord's responsibility to fix, so report it if you suspect it.

Attack the moisture at the source:

• Dry washing on an airer with a dehumidifier running, not draped over radiators or across the room
• Use the extractor fan and open a window while cooking and showering, and keep lids on pans
• Close the bathroom or kitchen door while moisture is being made so it does not spread through the flat
• Wipe condensation off windows and sills each morning before it soaks in
• Keep rooms gently and evenly heated rather than blasting heat then letting them go cold

This is worth getting right before you do anything else, because the three have different causes and only one of them is yours to manage.

Condensation appears on the coldest surfaces: windows, the inside of external walls, the corner behind a wardrobe, the back of a sofa pushed against an outside wall. It is worst in winter, it is often seasonal, and the mould that follows wipes off the surface rather than coming out of it. This is the type you can usually fix yourself.

Penetrating damp is a defined patch that gets worse after rain and does not move with the weather indoors. Look for a blocked gutter, a cracked seal around a window, or a shared wall on the weather side of the building.

Rising damp shows as a tide mark up the bottom of a wall, usually no more than about a metre, sometimes with salt deposits and blown plaster. It is rare in upper-floor flats and it is never a ventilation problem.

If it is not condensation, no amount of airing the flat will fix it, and the next two sections matter more than the dehumidifier.

Yes, and it is the most effective single device for it. A dehumidifier pulls excess water out of the air before it can settle on cold surfaces, so windows stay clear and mould loses the damp it needs to grow. A 12L model with a laundry mode is ideal for a flat, because it also handles the big moisture spike from drying clothes indoors. Because it just plugs in, it needs no permission and moves with you.

Plenty of older conversions have no mechanical ventilation at all, and nothing can be installed without the landlord's agreement. The workable answer is to move the moisture out at source and dry the rest of the air mechanically.

Shut the door of whichever room is producing the moisture and open its window, so the moist air leaves rather than spreading through the flat. Ten minutes with the window fully open moves more damp air than an hour on the vent latch, and cools the room far less than it feels like it should.

Keep furniture a few centimetres off external walls so air can move behind it, which is where the mould you cannot see tends to start. Where an internal bathroom has no window at all, a dehumidifier run in the room with the door closed after showering does the job a fan would have.

A plug-in dehumidifier is also the one intervention that needs no permission and leaves no trace, which is why it suits renting. Ours on the Meaco Arete One covers what to look for in a quiet model for a flat.

Treat visible mould promptly and then keep the room dry so it does not return. Wipe small patches with a proprietary mould remover or a mould-killing spray, wearing gloves and ventilating the room, and wash affected soft furnishings if you can. The key is that cleaning alone is temporary: unless you also cut the moisture with ventilation and a dehumidifier, the mould comes back. If it is widespread or keeps returning despite your efforts, report it to your landlord, as persistent damp can be a disrepair issue.

The split is clearer than most tenancy arguments suggest.

Government guidance on repairs in a private rental puts the property's structure and exterior on the landlord, along with heating and hot water, sanitary fittings and their pipes, electrical wiring, and - the one that matters here - "gas appliances, pipes, flues and ventilation". A broken extractor fan, a failed window seal or water coming through the fabric of the building is a repair, not a lifestyle issue.

Tenants are responsible for damage they or their guests cause, and should only carry out repairs the tenancy permits. That is the line landlords lean on with condensation: if the fan works and the windows are sound, the moisture is coming from how the flat is being used.

The same guidance is explicit that you should contact your landlord if the property needs repairs or has mould. If they do not act, the route is your local council's environmental health department, which can assess the home under the Housing Health and Safety Rating System. Keep paying rent while you wait: withholding it does not strengthen the case and can weaken your position.

Put the request in writing and date it. Photographs with visible dates, and a note of when you first reported it, are what turn a disagreement into a record.

If you rent from a council or a housing association in England, damp and mould now come with legally enforceable deadlines. This does not apply to private tenancies.

Awaab's Law (the Hazards in Social Housing (Prescribed Requirements) (England) Regulations 2025) took effect on 27 October 2025 for the social rented sector. The government guidance for social landlords sets out the Phase 1 timescales for damp and mould.

Two practical consequences. Reporting in writing starts a clock that did not exist before, so the date you reported it is now the single most useful thing to have on record. And the regulations are being extended from October 2026 to a wider set of hazards including excess cold, so a cold, damp flat may fall under more than one head in future.

It can, and it is one of the more commonly disputed deductions, which is exactly why the paperwork matters more than the scrubbing.

A landlord may deduct for damage beyond fair wear and tear, and mould-stained sealant, blackened plaster or a ruined mattress can be argued either way. The argument turns on cause: if the flat had no working extractor and you reported it, that is a repair issue; if the fan worked and washing was dried on radiators in a sealed room all winter, the landlord has a case.

Three things protect you, and all three are free. Photograph every room at check-in, including window reveals and the corners behind furniture. Report any damp in writing as soon as you see it rather than at the end of the tenancy. And keep the replies. Deposit schemes adjudicate on evidence, and a dated report beats a recollection every time.