By far the most common cause of black mould appearing on walls is condensation, moisture laden air settling on cold surfaces. As hot air (steam) rises in a building, this usually appears worst in the higher parts of the house in bedrooms and bathrooms and on clothes in wardrobes which may develop a musty smell.

The true cause is complex but falls into two parts: either it’s the tenants’ fault, allowing excess steam to form and escape into the whole house through cooking, washing and drying wet clothes, or it’s the property itself having too many cold surfaces due to lack of effective insulation or insufficient heating. This complexity makes it very difficult to pin down the blame exactly on either the landlord or the tenant.

According to recent research carried out by energy switching comparison website Uswitch, as temperatures drop, around 62.5% of tenants have revealed they’ve experienced some degree of mould in their rental accommodation.

With this statistic in mind, Uswitch analysed the prevalence of mould across Britain and some of the potential causes.

Some key statistics revealed:

  • 64% of those who’ve experienced mould were tenants in privately rented, council, or student accommodation.
  • Two thirds of Brits believe mould is solely the landlord’s responsibility.
  • 2 out 5 tenants claimed they wouldn’t clean mould themselves.

For those that have had mould:

  • 40% stated that they dried their clothes indoors.
  • 21% had furniture directly against walls.
  • 22% leave the kitchen or bathroom door open when cooking or showering.
  • 12% admitted to having a cluttered home.
  • 11% confessed to keeping the shower curtain folded when wet.
  • and 6% leave spillages.

The UK’s mouldiest cities:

The Uswitch research indicates which UK cities have the highest prevalence of mould:

Uswitch Research

Sarah Broomfield, energy expert at, identifies the financial struggles of paying for heating as a major cause:

“It’s unacceptable that so many struggle to pay their heating bills. Those avoiding putting their heating on in fear of unaffordable costs, may inadvertently contribute to the growth of mould in their home”.

“With the findings that the majority of those who experience mould are tenants, it’s advisable that they contact their landlord to come to an agreement on how to tackle it. Tenants should also be aware that if they pay the heating bills themselves, they have the right to switch energy suppliers to find a cheaper deal.”

“Whether you’re a homeowner or tenant, if you find you’re struggling to pay your energy bills, there’s plenty of help out there — from government grants to supplier support,” says Uswitch.

It is a fact that inadequate heating leads to condensation and mould in a property. It is also a fact that many tenants fail to heat their accommodation adequately because of cost, but the cost of heating adequately, enough to prevent condensation and mould, can be increased considerably when the house is poorly insulated or the heating system is inefficient.

Older properties with solid uninsulated walls, which predominate in the rental sector, invariably cost far more to heat to an adequate standard than a modern building, and therefore they are prone to suffer most from condensation and black mould.

For a couple of years now it has been a requirement under the Minimum Energy Efficiency Standards for all new tenancies or tenancy renewals of properties rented in the private rented sector to be brought to a minimum energy performance rating of “E” on an Energy Performance Certificate.

Landlords are now being encouraged to exceed this minimum to at lease a least “C” which would considerably reduce the prevalence of complaints about mould.

Methodology: Uswitch surveyed 2000 adults across the UK asking 20 questions on the subject of mould.

Dampness & Condensation

How to Prevent Tennant Complaints about Damp, Mould & Condensation


  1. Tenants never believe they are responsible for damp or mould & yet a property can go for years without either & then suddenly develop a problem.

    Renters who have never been homeowners may not understand how to prevent these issues as it is not their investment at stake & it is just easier to blame the landlord.

    Clearly some properties do have a problem & here LLs should make improvements but if a tenant ‘always’ has damp / mild problems wherever they live you have to be looking at lifestyle as the cause.

  2. My tenant complained of black mould. I went round and there was a lot of black mould. I advised her to air the house by opening the windows to let the damp air out, and to open the kitchen window to let steam out etc, and drying clothes on the radiators will mean water gets into the air …… and so on. She said she opened the windows and that she never dried clothes on the radiators.

    I drove past the property on several occasions and the windows were never open. Eventually the tenant moved out. It was clear that she never opened the windows as there was black mould on the handles which wouldn’t have been there if the handle had been used. There were items of clothing behind the radiators – a clear indication that she’d been drying clothes on them.

    I now have a new family in the property and there’s no problem with mould.

    A landlord can do their best, but if a tenant won’t comply then the problem will continue.

  3. My tenant reported ‘damp’ in a top floor flat which is condensation mould. He says he cannot afford to turn the heating on…and yet is brewing several vats of cider. It is so depressing to see a property being wrecked and being unable to do anything about it (well, not for several months yet)

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