It’s that time of year landlords dread: their tenant complains about dampness in their home and expect the landlord to do something about it, but what?

Nobody wants to live in a damp home. It causes mould on walls, furniture, bedding and clothes and it creates an unhealthy environment.

There are three main causes of damp:

(1) rising damp which emanates from the foundations up and shows itself on the lower parts of ground floor walls , skirting, floorboards etc. and if left unchecked can lead to wet and dry rot in floor timbers.

(2) penetrating damp which result from faults in the structure of the building, leaking roofs, gutters, downpipes, window frames etc. This can also damage the fabric of the building if left unchecked and again can result is wet and dry rot.

(3) condensation, perhaps the most common cause of black mould and mildew on fabrics, clothes and wallpaper.

Points one and two are problems for the landlord to see to without delay. The landlord is under a legal obligation to maintain the fabric of the building which provides a safe, warm and dry home.

Condensation is slightly different because although it can be caused by problems with the building it is also something which may be caused by the actions of the occupants – the tenants. That’s why it is so difficult to deal with for landlords.

Older buildings with limited insulation are more susceptible to condensation than modern fully insulated buildings, but any building can be affected if the conditions are right, even newly built ones. In fact new-builds are often more like an air tight box, so poorly ventilated and new plaster takes some time to fully dry out.

Condensation occurs when moist air comes into contact with a cold surface like a wall, window, mirror, wallpaper, clothing and fabrics etc. Warm air rises so it is more often the tops of walls and ceilings which are affected, usually in upstairs rooms like bathrooms and bedrooms.

The warm moisture-holding air can’t hold the moisture when it hits cold surfaces and it deposits tiny drops of water. When there is still air, like the corners of rooms, behind furniture or inside wardrobes the problem will be worse.

The usual causes are when steam is produced from cooking, drying clothes on radiators, baths and showers, where the steam produced is not immediate vented to the outside.

Condensation and black mould is unsightly and can cause health problems, so tenants may need to be “educated” as to methods of preventing condensation:

How to reduce damp and condensation in the home, what the tenant can do:

(1) Produce less moisture and make sure it is vented to the outside.

Simple things will make a big difference, like opening a window when cooking and showering, keeping the doors closed to prevent moisture spread throughout the house, keeping the lids on pans when cooking and using cooker extractor fans, drying clothes outside (and especially not on radiators), venting tumble dryers to the outside. Paraffin heaters or flue-less bottled gas heaters produce a lot of excess moisture. Landlords can help here by providing automatic ventilation fans in kitchens and bathrooms. These come on automatically when they sense steam / moisture.

(2) Maintain a reasonable level of heat. A cold house leads to cold surfaces which absorb moisture. By maintaining a good level of heating in the home the surfaces will not absorb the moisture and therefore there will be little on no condensation. Heating, coupled with good ventilation at the source of the moisture will cure most cases of condensation completely.

Invariably, in bad cases of condensation the tenant is scrimping on heating and because the house is so cold is reluctant to ventilate. I’ve even seen cases where ventilation ducts and trickle vents are blocked to prevent drafts because the house is so cold. This coupled with drying clothes indoors and all the other sources of moisture generation leads to a vicious circle of more cold, more moisture penetration and more condensation.

Once this cycle is started the fabric of the building absorbs the moisture and in extreme cases timber, plaster and masonry are damaged permanently. Also, once the spores are established the mould will quickly return every time the right condition are present even when deep cleaning has occurred.

How to reduce damp and condensation in the home, what the landlord can do:

(1) Make sure the building is free from external defects, rising and penetration damp.

(2) Make sure the home is insulated to modern standards meeting the latest Energy Efficiency Standard of E or above.

(3) Make sure the heating system is up to standard and is reasonably efficient to run – tenants will avoid using energy if it is costing them too much.

(4) Provide extractor fans which are an effective way to get rid of moist air and steam so that less condensation forms. Some very modern homes have extractor fans which are automatic or run continuously, fitted in the ceilings of kitchen, bath and shower rooms.

(5) Provide door closers to keep moisture confined to where it is generated.

(6) In extreme cases think about a fully forced ventilation system where an air pump in the attic continually circulates the air.

(7) Provide written information to educate tenants as to how they can minimise the problem.

How to get rid of black mould

If the home is already affected by black mould after a long period of condensation build-up, it needs to be properly cleaned with a spray containing bleach. Wear a mask to prevent inhaling mould spores which are dangerous to health. After the area is dry it should be sprayed with an anti-fungal wash and allow that to dry again – follow the manufacturer’s instructions.

You can also treat the affected areas with mould-resistant paint, available from most major hardware stores, but this should not be necessary if the problem is properly cured.

Images of black and unsightly mould in the corners of rooms are always the focus of TV documentaries and reports on the housing conditions that tenants are living in, and almost always the blame for this is put at the landlord’s door. A proper understanding of condensation and mould and its causes shows that very often it’s caused by the lifestyle of the tenants, and its only they who can do something about it.

A typical scenario goes like this:

“I have noticed black patches on the wall paper, mould on my clothes in the wardrobe and a damp musty smell throughout the house but particularly upstairs. Landlord, what are you going to do about it, are you going to compensate me for the damage to my clothes?

“I’ve asked a damp specialist who tells me there’s definitely damp in here, so it’s not just me saying this, can we get someone in to deal with it?”

A few points to consider if you are faced with this:

Condensation, damp and mould is a very complex issue and it’s not always obvious what the cause is and who should be held responsible, so you should avoid jumping to conclusions as to whose fault it really is.

Also, it must be born in mind that advisors on damp often have a vested interest in finding a problem, which they can then be contracted to “cure”.

If it comes to legal action and blame, enforcement has just as often been against the tenant as it has against the landlord when with expert witnesses cases have come to court.

Unless a specific cause can be identified for the dampness such as leaking roof, walls, gutters, drains, water pipes or rising damp, the black mould is more often than not caused by condensation – air born water vapour.

Condensation in turn is sometimes caused be inadequacies in the building construction, such as poor ventilation, insulation and inadequate heating systems and older properties are more susceptible because they generally require more heating and suffer greater heat loss.

A full investigation should be carried out and if necessary a temperature monitor can be installed to check the average level of heating which should not fall below 18 degrees minimum.

If the issue results in a dispute it is useful if landlords have a record of the history of the property; have previous occupants experienced the same problem, or is this down to one tenancy?

For an in-depth discussion on this topic see this article: https://www.landlordzone.co.uk/pdf/Mould.pdf
Any questions on this issue, see the LandlordZONE Forums: https://forums.landlordzone.co.uk/


  1. I believe rather than cleaning with bleach – which can in fact cause the mould to come back – an anti fugal wash is the correct treatment.

  2. I experienced condensation mould in 2 bedroom flat the first winter after the tenants moved in. some condensation mould was reported by previous tenants (5 years) but not as much as new tenants. I called damp experts who only quoted me in several thousands to sell their own products that involved drilling holes in walls various parts of the building. After some online research, I found Nuaire drimaster positive input ventilation unit, researched the best product suited for my property, bought it for £400’ish though an online retailer, installed it myself being qualified electrician and have had no issues reported this winter. Installation took max 2 hrs and very easy and straight forward. It can be set to run during winter conditions or all year round. It is tamper proof so tenants can not adjust settings. Consumes negligible amount of power. Tenants are happy saying flat feels so fresh throughout. win win situation as I did not want to see the tenants leave or evict them and it’s a long term solution to problems experienced with tenant lifestyle.


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