Tom’s top tips on condensation and mould

Tom Entwistle, a residential and commercial landlord since the 1970s and founder of LandlordZONE, offers a landlord’s perspective on a topical issue. In this article, Tom shares his insights on damp, mould and condensation in rental properties.

For more information, you can also read Total Landlord Insurance’s ultimate guide to identifying and preventing damp, mould and condensation in your rental property and mydeposits article on how to avoid deposit issues at the end of the tenancy relating to damp, mould and condensation.

How I deal with damp, mould and condensation in let properties

Condensation is a perennial problem for landlords. We’ve all seen those pictures of horrible black mouldy walls whenever the media gets hold of a story about how “evil” landlords are forcing their tenants to live in such dangerous conditions. Yes, sometimes that’s true, but more often there are other reasons for this sorry tale.

I’ve experienced the problem personally several times throughout my landlording career. Winter comes along and you get a phone call from a tenant complaining about “damp”. One in particular I recall. When I arrived at the property I was greeted by a rather angry young man who was staying in the house by himself. He was complaining bitterly about the musty smell, and the damp and mould on his clothes in the wardrobe.

We went upstairs together and I distinctly felt how cold it was. I wondered how he could sleep there. Sure enough his clothes had a damp musty smell and there were spots of mould on them. At the time I was mystified. I’d had many tenants in there before him and no one had ever complained about this sort of thing. As I was leaving downstairs I caught, out of the corner of my eye, the sight of his radiators, and a wall storage heater, all covered with his clothes.

Not being experienced, it was only when I started to do some research that I could put the clues together. A very cold house – he was scrimping on heating – and drying clothes on radiators, classic causes of condensation. There was no structural damp in the property, no rising or penetrating damp or leaks, the property was sound, it was purely condensation damage.

In this case I was being blamed because of the actions of this one tenant. Other tenants had lived in the property before perfectly happily without causing condensation problems, but here I was, confronted by this angry young man in his bedroom, being asked to compensate him for a wardrobe full of smelly and mouldy clothes.

What causes condensation?

Condensation occurs when humidity levels in the air are high, in other words when steam condenses on cold surfaces. It will naturally condense mostly on window glass and mirrors, but if it’s cold enough, on walls, even on bedding and clothes in wardrobes.

If the situation goes on long enough – producing excessive amounts of steam from cooking, washing, showering in bathrooms and drying wet clothes indoors – then moisture will penetrate deep into the fabric of the building, wallpaper, plaster and masonry. It will lead to crumbling plaster, plus wet and dry rot in timbers. It leads to a vicious cycle where the embedded moisture makes the house even colder, leading to even more condensation.

What’s the answer?

There are three things to do that are guaranteed to prevent condensation in any home:

(1) provide adequate heating that will warm the fabric through. Warm walls won’t provide a surface where water can condense, soaking into the fabric, and therefore no black mould will appear. You just don’t see condensation mould in a warm home period, as the Americans say!

(2) Ventilate steam at source and prevent it circulating through the home. Automatic extractors in kitchens and bathrooms are great for tenants who won’t do this, these sense humidity levels and remove the steam automatically without it travelling through the home. Even so, the doors should be kept closed – steam rises so it’s always the upstairs rooms, which are usually cooler anyway, that are most affected by condensation.

(3) Don’t bring in wet clothes or try to dry them indoors, unless this is done in a condensing tumble dryer or one with an outside vent.

The problem is, most of these measures are outside of the landlord’s control.

The energy cost crisis

Heating is going to be a big problem this winter; the cost of fuel is going to make everyone think twice about having the heat on too high. With central heating it’s usually best and most economical to have the heating set on a low level continuously. That way there’s no need to keep re-warming the house from cold when you come home, and it prevents the temperature ever falling to a level where pipes can freeze up.

As a landlord it’s incumbent upon you to provide a heating system that’s effective and reasonably economical to run, otherwise your tenants will inevitably scrimp and try to save, and you’ve seen the consequences of that. A new boiler will set you back around £2,000 but it will be economical to run, it will meet the new Decent Homes Standards and the EPC standards, which are likely to be set at a minimum of “C” rating soon.

It’s no use having an efficient heating system if all the expensive heat disappears quickly through the roof, walls, floor and windows, or there are excessive draughts caused by badly fitting doors and windows. All these elements need to be properly installed and insulated to modern standards to keep the heat in the envelope of the home, while still providing the necessary amount of ventilation when and where required.

In extreme cases the fitting of a full air recirculating and heat recovery ventilation system can be installed, but this is obviously quite expensive and is best done when the house is being built or during a major refurbishment.

Older properties – and these predominate in the private rental sector – often have solid walls with no cavity, which are far more difficult to insulate properly. These need extra work and expense to bring them up to modern standards, but landlords may be forced to do this in the near future.

These are things that are within the landlord’s control, all of which cost money, but if you are to make money from letting property then you should be prepared to invest money into it in the first place, to make sure your tenants are safe and warm.

What can tenants do?

Reduce the amount of steam produced when cooking by covering pans, using a cooker hood extractor and don’t have water pans and kettles boiling too long. Don’t use or minimise the use of paraffin and other portable heaters like LPG gas, which all produce a lot of moisture. With portable flue-less bottled gas, one gallon of gas or paraffin produces about a gallon of water.

Never dry clothes indoors, if you must do this put them in a vented bathroom with the door closed.

Modern homes are virtually hermetically sealed, but some ventilation is required to keep the air fresh and get rid of the moisture produced, simply by people breathing. Trickle vents above windows including bedrooms should not create draughts and will be adequate for this job if used properly.

Kitchens and bathrooms need much more ventilation when washing, bathing or especially if drying clothes. This is where the extractor fans are needed, either controlled by the light switch or automatic humidity sensing.

Keep doors closed in rooms like kitchens and bathrooms when in use. Don’t have furniture too close to the wall, allow some space between the back of a wardrobe for air to circulate. If there is a problem with cold air and musty smells, leave the doors on wardrobes and cupboards open.


Sometimes tenants will create condensation problems because they don’t understand what causes it, after all it’s not all too obvious, and that’s why landlords get blamed. You need to educate your tenants, especially young and inexperienced ones, by explaining what they need to do to minimise the chances of getting condensation, and in a really cold winter, burst pipes. I always provide a written guide as well as a verbal explanation, given when winter is approaching. Total Landlord Insurance has produced a damp and mould tenant’s checklist which you can download and include in their information / welcome pack to help tenants understand the steps they need to take to avoid damp, mould and condensation

Difficulties arise when tenants won’t cooperate. They block up vents to prevent drafts because there is no heating, they skimp on heating, they produce too much steam and allow it to circulate. I’ve even heard of a tenant refusing to minimise steam or close doors, or remove condensation from windows, blaming the landlord and demanding that the landlord send someone round to do this for her.


Condensation problems can result in disputes which may even end up in court. Local authority housing officers and environmental health officers may inspect the property following tenant complaints. If you are unlucky enough to get an inexperienced officer they can easily mis-diagnose the problem, mandating work be done that’s not necessary. I remember one case where the local authority officer demanded that a full bay window and wall be replaced because there was black mould on and all around it.


Faced with a dispute or a prosecution by your local authority, as with all disputes in court, good evidence is the key to the success of a good defence. If you are confident that your property is not at fault, evidence might be, for example, an independent surveyor’s report, temperature monitoring over a period, and I like to survey all my tenants when they leave. If you have a long series of surveys showing that there were no complaints about condensation and black mould, that’s really powerful evidence that it’s not your fault.

Some questions and answers:

Who is responsible for damp, condensation and mould – the tenant or the landlord?

The landlord’s responsibility is to ensure that the structure, fabric, insulation, heating and ventilation systems in the property are adequate to provide comfortable living free from cold, damp and condensation. It’s the tenant’s responsibility to take positive measures to prevent unnecessary condensation, because this action is out of the landlord’s hands. 

What is often overlooked is that a lot of damage can be caused to a property if condensation occurs over an extended period. So, when it can be shown that it’s the tenant that’s at fault, easier said than done, they could in theory be held liable to pay damages to the landlord.

What can a landlord do if the tenant refuses to cooperate to prevent condensation?

If your tenant won’t do what’s required to be done to prevent condensation, after repeatedly being told, then that’s very frustrating for the landlord, and the tenant is likely to be suffering as well. Sometimes it’s simply down to the fact that the tenant cannot afford to heat the property properly, it’s a very common cause and it’s worrying because of the long-term damage it does to the property and to health.

What can you do? Well one option is to seek a court injunction – where a court orders someone to do something or not do something – but in my view that’s far too involved and costly and might not work anyway.

Unfortunately it may reach a point where eviction is necessary. Currently, with Section 21 this is relatively straightforward, though a lengthy process – six to nine months usually. However, if Section 21 is banned, as is likely soon, you’ll be in the unenviable position of having to convince a judge that your tenant is slowly destroying your rental and you need it back!

How do you deal with damp in a flat when you’re not the freeholder?

Good question, as they say! It depends on the nature of the dampness. Is this structural, in which case it’s down to the freeholder and dealing through the managing agents to get repairs done, or is it a condensation problem, in which case you’re in the same position as with any other letting. And of course, there’s always the cases where it’s a combination of the two causes. That is, there are defects in the structure, condensation is being caused through lack of good insulation making the flat too cold, and the tenant is being neglectful of preventing condensation as noted above.

How do you know you’ve got your diagnosis right?

It’s important to get your diagnosis right so that your treatment solution can be effective. Rising damp, penetration damp and internal water pipe leaks are all the responsibility of the landlord, but sometimes these are difficult to diagnose and cure. One example of this difficulty springs to mind: an internal water pipe joint was leaking but because the pipe had a slight slope, water was running along its length and the damp appeared 20 feet away.

On the other hand, condensation problems are obvious to experienced eyes but not so to the inexperienced, as I’ve explained above. Often this is down to the lifestyle of the tenants, but not always, or again it can be a mixture of both tenants and the state of the property.

Getting an accurate diagnosis and cure using a damp specialist is not always straightforward in my experience either. Before I learned how to identify these issues I used specialists. But it’s a bit like asking a hairdresser if you need a haircut: they have a vested interest in finding a problem, which they may or may not cure after an expensive “repair”.

The local council will come down on landlords when they receive complaints, but unfortunately not all inspectors have enough experience to distinguish between the different types of problem, as I’ve said above. It’s probably best to use a good chartered surveyor with a lot of experience under their belt, if you don’t have that experience yourself.


There’s more detail about how to deal with damp problems in the LandlordZONE article here, but it’s important to get to the real cause and deal with it properly, just painting over black mould is definitely not the answer.

Cold and damp are very uncomfortable conditions in which to live, and in this day and age nobody should have to endure such conditions. Unfortunately in the real world many people in rental homes do. Around 20 per cent of all rental homes fail to meet the Decent Homes Standard (currently under review) and many of these suffer from damp, condensation and mould.

This year in particular, in the middle of an energy price spiral, these sorts of conditions in homes are likely to get worse. Why? Because one of the main causes of condensation and mould in a home is lack of heating. After rent and eating, heating and lighting are the biggest expenses and ones that are likely to get cut back.

For more advice on this topic, listen to the latest episode of the property cast, Demystifying damp, mould and condensation for landlords and agents, hosted by Sean Hooker, Head of Redress at the Property Redress Scheme and Paul Shamplina, Founder of Landlord Action. The pair are joined by Suzy Hershman, Head of Disputes at mydeposits and Julie Ford, HF Assist Advisor. Tune in to hear their insights on the myriad of issues surrounding this common problem for landlords and letting agents alike.

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