Viewpoint by Tom Entwistle

As winter approaches outside temperatures drop and the perennial landlord’s problem of winter condensation and black mould rear their ugly heads again.

The question is, how do you know if this is caused by the building or the tenant, or is it a combination of the two?

Dampness or condensation symptoms are very similar but the cures are very different, and to the uninitiated applying the wrong methods can be both expensive and ineffective.

When tenants start to complain about “damp” to their letting agents and landlords, you need to have some answers.

What’s more, condensation and damp have a bearing on evictions and in particular the issue of the so called Section 21 “revenge eviction” which landlords need to be well award of.

  • What causes condensation?
  • Is it the same as dampness?
  • Why is it that some tenants have condensation problems while others don’t, even in the same property?
  • Why is it that condensation problems are more prevalent in rented properties?
  • Why are older properties affected more than modern ones?
  • What effective measures can be taken to solve this problem?
  • What can landlords do if they are taken to court over this or when rent arrears tenants claim in court they don’t pay because of dampness?

I’ve had many years dealing with these problems in residential as well as commercial properties and in that time I’ve begun to develop a good understanding of this tricky problem and how to deal with it – in this article I will attempt to answer these questions and provide some solutions.

Despite many articles I’ve seen written on the subject, it’s not generally very well understood.

There’s a lot of misunderstanding around it, and even some so called “experts” get it wrong.

Mention damp and black mould, and we’ve all seen those nasty pictures in print and in the television documentaries, and immediately the landlord is denounced; he or she becomes the pariah figure who is condemning tenants to live in appalling health-threatening conditions.

Yes, it’s true that some properties have such serious defects that they are prone to damp and condensation and their owners need to put them right.

But far more common is a situation where the root-cause of the problem is the way the tenants are living, or sometimes it’s a combination of that and inadequacies with the property.

The problems landlords have is that tenants, the general public, environmental health officers (EHO), solicitors and judges in court, very often just don’t understand the difference between damp and condensation, their root causes, and who is really at fault.

What causes condensation?

Tenants often report dampness in a property when in fact the black mould on the walls and musty smells on clothes are caused by condensation.

Condensation occurs when warm moisture laden air meets a cold surface. Typical is when steamy air from cooking, washing and drying clothes rises up to the top of the house and meets a cold surface; easily visible as water droplets on window pains and tiles, but less so when the moisture meets cold wall paper, plastered walls, carpets and clothes in wardrobes in unheated rooms. Then it is invisible, quickly absorbed into these materials and results in that cold musty smell and mould spores.

So, there are two main causes of condensation:

1 – Too much steam and moisture laden air that rises through the house rather than being vented outside at source; usually from the kitchen or bathroom, or typically when clothes are left to dry on radiators.

2 – A house with rooms that are far too cold.


When steam is produced it should be vented out of the house in the room where it is produced, by opening windows, using permanent vents or extractor fans, and closing doors to prevent it circulating round the house.

The problem is that opening windows in winter is not something people want to do as it cools the room, and providing permanent air vents does the same thing. I’ve seen many vents purposely blocked with rags by occupants.

It does not help that the modern house, with all our draft proofing measures, unlike the old days with chimney ventilation, becomes a hermetically sealed box, so even new houses suffer some condensation.

Rooms too Cold

It’s always the coldest rooms where condensation happens and black mould appears, usually tops of walls in bedrooms which receive the least heating.

Very often it’s simply a matter of not providing enough heat in the house, either to save money, because the occupants can’t afford to heat, or because the heating system is not up to it.

When the house is poorly insulated, as in many older properties without cavity walls, heating is expensive because a lot of it is being wasted. Then, lack of heat leads to colder and colder moisture absorbing walls and more and more condensation. It becomes a vicious cycle.

Tenanted properties are particularly prone as most tenants are trying to economise; out all day they have little or no heating, then in the evening they blast the place with steam from cooking and washing.

A really well insulated and heated house will rarely suffer much condensation because everything including carpets, wall paper and clothes in wardrobes are all nice and warm and will not absorb moisture, even when some steam is generated.

Interstitial Condensation

A technical term used to describe what happens when condensation remains a problem for a long time. The cold walls absorb more and more moisture which penetrates deep into the walls; the wall paper, plaster and masonry, and even timber, which will eventually lead to dry rot. The moisture is so deep it will take months to dry the building out, even when more than adequate heating is applied.

Likewise mould spores will develop on surfaces which eventually become toxic (causing a real health hazard) and are hard to eradicate.

So, once these conditions have been allowed to develop they can be very difficult to reverse; they do a lot of damage to the fabric of the building and they are a serious health issue for occupants and anyone attempting to clean up.


Dampness is different to condensation and has different causes which are invariably defects in the building and most definitely a landlord issue. These are not difficult to spot and eliminate: a leaking roof, gutters and downspouts, rising damp in the lower parts of ground floor walls and floors in basements, or a leaking water pipe. All these will create a localised problem and will appear different to condensation and mould.

Older properties and insulation

Many rental properties fall into the older category and are without cavity walls and modern insulation standards. The Energy Performance Certificate (EPC) gives an indication of this when a tenant enters into a tenancy.

The Government has announced changes to the Energy Bill to include a new law introducing a legal minimum energy efficiency standards for homes rented from landlords from 2018. They have also announced the introduction of measures from 2016, to allow councils and tenants to demand energy efficiency measures from landlords.

This means that one-in-ten buy-to-let homes will be unlettable in four years’ time unless their landlords take steps to improve their property’s energy efficiency.

Tenants will also be able to demand improvements to insulation from 2016, when landlords will not be able to refuse tenants’ “reasonable” requests for energy efficiency measures.

The legislation states that landlords must not let out properties with the two lowest energy efficiency ratings, F and G, after April 2018 at the latest. According to a recent English Housing Survey, 11.4pc of homes in the private rented sector were rated F or G in 2011.

The flagship government-backed loan scheme, The Green Deal, to help people give their homes green makeovers has been “disappointing”, the UK energy and climate change secretary has conceded.

This, it appears, is because the funding is expensive relative to other ways of doing this, and in general landlords are advised to make their own arrangements for bringing their properties up to modern insulation standards before these legal deadlines come in and make the letting illegal.

Revenge Evictions

Revenge or retaliatory evictions have been in the news recently, and although it appears many of the claims that landlords evict tenants just because they complain of the need for repairs have been exaggerated, nevertheless it is an issue.

It has resulted in the Coalition Government supporting a private member’s Bill to be introduced by Sarah Teather, though an adverse response from landlording bodies has now prompted a Government short enquiry.

Her proposal is that the use of section 21 should be limited when environmental health officers (EHO) deem the property to have serious defects and health and safety hazards, damp, condensation and mould being one of these.

Really bad conditions are largely confined to a small proportion of rogue landlords who for the want of a better term, let slums.

But all good landlords ought to be concerned about the proposals because damp, condensation and mould is so difficult to pin down to a cause – it can just as easily be the tenant as much as the building and landlord.

The concern is that if not handled very carefully, this proposed change will adversely affect ALL landlords as it will bring in a fundamental change in the tenant-landlord balance in housing tenure law.

Currently two restrictions are imposed on the section 21 process: licencing and deposit rules. For both of these the landlord is still in control – follow the rules and they retain control, that’s fair enough. Sarah Teather’s change will take the control out of the landlord’s hands and give this to the judgement of Environmental Health Officers (EHO) and the courts.

This has the potential to cause serious issues for ALL landlords because:

  • (1) EHO judgements are sometimes suspect,
  • (2) Convincing a judge on repair issues is challenging to say the least,
  • (3) Both these services are seriously under resourced and currently cause long delays – add this extra workload, which could to be substantial, and chaos will inevitably ensue,
  • (4) Gaining access to rented property to remedy defects is often very difficult for landlords,
  • (5) The process is wide-open to abuse by those tenants who wish to avoid eviction by “creating” defects of their own.

By way of example: a recent case cited in the Letting Update Journal (Oct 2014) was of a tenant who refused to ventilate even though the radiators were covered in wet drying clothes. The property was covered in black mould even though it had been free of condensation problems with previous tenants. The tenant violently refused to follow advice and brought in the local authority Environment Health Officer.

After the inspection the EHO came up with a long list of modifications and “improvements” that the property needed, even though it had been fully refurbished before this tenancy, which included moving radiators, building a new internal wall and replacing a large bay window.

On appeal it seems the report was modified with more emphasis placed on the tenant’s responsibility in the issue, but nevertheless it illustrates the difficulties landlords will face with inexperienced EHOs, as this lady clearly was, if Sarah Teather’s rule becomes law.

In my experience a large percentage of the time condensation is caused by the tenant: (1) saving on heating costs and living in a cold house, (2) not ventilating when washing and cooking, (3) drying clothes on radiators etc.

Try to convince tenants, some EHOs, some judges and the general public that this is not the landlord’s fault and you are met with pure cynicism and you really are up against a serious lack of knowledge and understanding on the issue.

I’ve seen this problem develop with tenants from all socio-economic groups, so it’s not confined to the bottom end of the letting market. But often you will never convince the tenant or the authorities of the real cause unless they are experienced or you can show that previous tenants in the property never had an issue with condensation.

My concern with the Bill is that there is a danger of introducing a process where good landlords just cannot get fair treatment; cannot easily resolve these situations quickly when it’s costing them money in repairs / rent payment disputes, and where, given time, landlords will simply realise that letting is just not worth the hassle.

Damp specialists

Beware the damp specialists who come into a condensation riddled property with their two pronged meter, showing you just how much dampness the wall contains. Of course it does, because the condensation has well and truly soaked in over time, but their suggested remedies will often be very expensive and ineffective.

Advice for your tenants:

The incidence of condensation can be reduced by:

  • 1. Leaving background heating on all day in all rooms and generally making sure the house is adequately heated in cold weather. Insufficient heating is the main cause of condensation in rental properties.
  • 2. Opening a window or using cooker and wall extractor fans when cooking and keeping lids on saucepans.
  • 3. Leaving bathroom doors closed and the windows open after a bath or shower to clear steam.
  • 4. Keeping the bathroom door closed when washing, bathing and having a bath or shower.
  • 5. Never blocking air vents or airbricks.
  • 6. Opening windows in all your rooms for a short period each day to allow some fresh air circulate.
  • 7. Never drying wet clothes on radiators or storage heaters.
  • 8. Never introducing portable LPG heaters – they produce 1.6 litres of water for every kg of gas burned.

Advice for landlords

  • 1. Make sure the property is free from issues that can cause dampness – leaking roofs, gutters, down-pipes, rising damp, bridged damp courses, leaking pipes, blocked drains etc.
  • 2. Make sure the property meets modern insulation standards – you will need to bring your property up to standard before 2018, so you may as well do it sooner rather than later and avoid problems with condensation.
  • 3. Make sure the heating system is adequate for the property and is well maintained.
  • 4. Consider fitting extractor fans in kitchens and bathrooms and trickle vents in window frames. These vents can be of the automatic types which operate when humidity levels rise, but remember, people will block these up if they feel the cold.
  • 5. Send a Condensation Letter (see our Documents Section) to your tenants advising them how to avoid this in the winter months.
  • 6. In extreme cases think about supplying a dehumidifier which will remove moisture and dry out rooms.
  • 7. Beware when cleaning black mould as the pours can be toxic and a major health hazard – seek professional advice from a cleaning specialist with the safety right equipment.
  • 8. The ultimate cure when tenants won’t cooperate is a full house loft mounted air re circulation system with heat exchangers which provides a continuous flow of fresh, warm dry air throughout the building.

Advice for Disputes

Landlord-tenant disputes are unfortunate but an occupational hazard for all landlords. It’s also unfortunate that many tenancies start off really well and over time deteriorate into poor relationships for no particular reason apart from resentment creeping in, for one reason or another.  As Robin Williams said in the film Dead Poets Society, “…T’was always thus, and always thus shall be!”

Relations can get very strained and when a certain point is reached, persistent rent arrears and late payments, damage to the property, or anti-social behaviour, for example, it is not unreasonable for a private landlord to start eviction proceedings. Social landlords can afford to be and usually are much more tolerant of all of this; private landlords usually can’t afford it.

However, tenants will sometimes bring up issues in a defence against eviction. The defence can range from finding technical errors in the way the landlord has served notices, or completed court papers, to defects with the property, whether real or imagined, notified or not.

Under the present system the landlord can be faced with a defence immediately before or during a court hearing when it’s too late to do anything about it. Claims of disrepair will usually mean a deferred trial date, sometimes 6 months hence, with a request for expert reports on the conditions.

The up-shot is a long and expensive legal process is in train where the loser pays all costs.

10 key tips for resolving disputes and winning your case

  • 1 – When problems arise, such as rent arrears, damage to the property, introducing pets without permission etc., always contact the tenant quickly and discuss the problem.
  • 2 – Always document these discussions and all contacts with a follow up letter outlining the details of the problem, how it is to be resolved and an agreed timescale for this.
  • 3 – In the case of rent arrears send off a rent arrears letter (see the LandlordZONE® Documents section), a rent schedule and serve notices s21 and s8. Try to assist the tenant in overcoming the problem short-term by helping with Housing Benefit claims and re-scheduling rent payments.
  • 4 – Try to get a reason for non-payment in writing from the tenant – this goes some way towards preventing late on “invented” reasons as a defence against eviction if it comes to that at a later date.
  • 5 – In the case of repair issues, request access to the property for inspection and if possible have an independent expert (a builder for example) present and help you compile a report which can be compared to your ingoing inventory. Include photos if possible.
  • 6 – In the case of condensation, evidence from previous tenants can be crucial. If they had a good experience, try to get documentary evidence from them. Think about a leaving questionnaire for all tenants.
  • 7 – Inexpensive Temperature, Relative Humidity and Dew Points meters are now available which mean landlords can quickly check room conditions and provide evidence of this.
  • 8 – Taking gas and electricity meter readings can be useful to determine the amount of energy the tenant has consumed since they entered. A quick calculation can provide evidence of the average weekly consumption and therefore the heating applied.
  • 9 – Request access to carry out necessary repairs and get them completed as soon as possible.
  • 10 – Landlords should do their utmost to resolve problems without court action as most landlords do. It’s obviously in the landlord’s interest to keep tenants in their properties as long as possible, so long as they pay rent and don’t do damage.

Documentary evidence is the key to winning any court action – judges will not take a landlord’s word against that of the tenant, so you must back-up your assertions with good solid evidence. This will be even more important in future if Sarah Teather’s Bill becomes law.

LandlordZONE® Documents

Private Rented Sector Energy Efficiency Regulations

Revenge Evictions – short enquiry


  1. There are individual extract fans for kitchens and bathrooms that run constantly at a very low level, boosting when the light is on or there is high humidity. They are more expensive to buy than the standard models, but do at least ensure some ventilation and running costs are calculated under £5 per year. However it doesn\’t help with those tenants who will insist on switching all fans off.
    The other option, is the installation of positive input ventilation units. These bring fresh air into the property forcing old air out and can be very effective. They can also come with counters so that the landlord can tell if they have been switched off for long periods.
    Whole house systems with heat recovery are expensive and have to be maintained to get the benefit so usually only worth installing in well insulated buildings.

  2. And while the landlord runs about justifying xyz and providing help to the tenant and being persecuted by Environmental health they are not paid a penny for the work…as usual.
    I recently had a case. Whilst tenant was in hospital her kids must have had a wild party. Sealant pulled from around bath, toilet cistern broken, sink pulled off wall. Apparently there was also a leak on the waste under kitchen sink which was never reported and \’her father fixed it\’\’ . When tenant came out of hospital suddenly EH called in and place was viirtually condemned as being damp. Yep it was but no fault of mine. Fortunately property had been inspected by the council 6 months earlier and photographed as it had been totally renovated for sale (renting was inotially only for 6 months) . I refused to repair damage and told tenant to look to her family not me . I won with EH by the way.

  3. Agree with the above. In particular, positive input ventilation is very effective against condensation and mould related problems. I have fitted dozens of these units and every one, without fail, has cured the condensation problem. The added bonus is that the fan unit is loft mounted and hard wired, making if difficult for prying fingers to switch off!

    • If anyone as some advice, I\’d be really grateful.
      The vault in my basement flat has condensation issues.
      There is the very clean, tanked vault (under the road), leading via an archway into a well maintained vestibule (under the pavement, with glass bricks) containing the boiler, and a cupboard with gas meter, pipes and stopcock, and then a door into the main bedroom (which has an ensuite on the other side of the room).

      It seems fine when the door to the vestibule/vault is left open, but when closed there is no ventilation and the condensation builds up quite quickly.

      While it would be nice for me, I don\’t expect the tenants to have to leave the door open, it is perfectly valid for them choose to close it (and I certainly can\’t prevent it).

      The main source seems to be the small cupboard with gas meter, pipes and stopcock.
      It has been \”dealt with\” several times, but the problem never really left.
      The pipes are all well lagged, and the pipe entrance/exit areas have all been foam filled out to and including under the road, but the vestibule, and mostly the cupboard, still seems to \”sweat\”.

      I have placed one manual de-humidifier (the large tablet holding type) inside the cupboard, and another one outside the cupboard, on top of the boiler. When the door is closed, the de-humidifier in the cupboard soaks up about an inch of moisture (~400mls?) in about a week. The one outside the cupboard, much less.

      The glass bricks also seem to gather the odd water droplets, I\’m not sure if this is them alone (cold -v- warm)or because they are above the pipes/cupboard.

      There is a small radiator in the vestibule, I don\’t normally switch this on but wonder if that would perhaps help, or harm the situation?

      My main question is – would a PIV be a suitable option here?
      Or simply fitting some airbricks (there is no ventilation at all in the vault/vestibule area)?

      Thanks for reading, and all advice gratefully accepted!

      In the meantime, have a lovely weekend all.

  4. I am one of those officers you speak about. After 30 years in the business this is one of the best article and advice on condensation I have seen. I support the new bill on revenge evictions but caution is needed. I want to see landlords managing their properties like a business and not this is to my pension pot. Good knowledge about your property and don\’t just take the officer\’s opinion,it\’s your business and if you\’re good at it you don\’t need an inexperience officer or court telling you what to do. Keep your eye on the ball

  5. Hi Tom,

    Really well written article, practical and realistic in approach. It has been an issue in all most every property. I think there should be a clause in the AST for landlord and tenant to take steps to avoid condensation, it only it can be enforced. Thank you for sharing your expertise.

  6. Thanks great article. Regarding condensation, totalt agreed with lack of knowledge between damp and condensation and cause of mould even amongst those supposedly in the know. Please consult Graham Coleman\’s site remedial techincal services or Peter mc Donald\’s site. There is a weath of excellent material on their websites and they are top damp consultants/ surveyors.
    Separately, thepiv units seem excellent in more severe cases of mould. The fitting of the unit professionally varies in price depending on the part of the country. The last part, wiring must be completed by a professional electrician.

  7. I\’ve done about 6 months research into this topic of penetrating damp and condensation for legal reasons and been in contact with the top damp consultants/ surveyors in the UK (thanks). I\’ve read a few posts on this forum and it so frustrating that tenants blame any structural defects on mould as one cannot see \’moisture\’! Condensation tends to be a problem in 8-9/10 of cases where there is mould, typically in tenanted properties.
    Mould survives on the pure water in condensation (atmospheric moisture, see PCA material).
    The purpose of my post is to warn others of my experience. My tenant was insistent of penetrating damp from dislodged roof causing mould to clothing, shoes etc, even the appearance of that textbook t shaped mould growth pattern in the corner of a downstairs room (used as a bedroom) as far as one could get from the roof! Mould was also found in the typical cold spots window recesses, even the plastic blinds indicative of excessive atmospheric moisture.
    As in Mr Entwisle\’s article, I experience a suspect judgement from the EHO on a number of counts- his lack of knowledge of damp as exemplified by his inability to distinguish between penetrating damp and condensation (though he saw no mould inspecting out of condensation season and a few months on!) and that moisture from one area of the house will migrate to the coldest spots in the house by generating a water vapour pressure which diffuses via plaster/ wood and hence the need to open windows (dampdecay site, Peter McDonald). It\’s not rocket science, that\’s why bathrooms are tiled!
    My evidence was pretty strong and I chose to fight for a few months but stress and the thought of spending more time on this got the better of me, so I settled. Not satisfactory for someone who damaged my property. I feel I could write a story on this topic- I hope you folks have better luck and hope it is helpful to someone.

  8. We need a law to protect landlord from inexperience eho and also rogue tenants mostly English, not the foreigners. I had a proper door on one lodgers room and eho put it down to flimsy and lock not lock. its a lock and it locks. the other side was not key lock and was defective, so i had to wait for their new stock to arrive to exchange.

    I had a double glaze new sash windows and anyone with know how will know there is a non key lock to keep the windows open. yet eho put it down to low windows around 1100 mm height and require a jack lock at bottom of sash windows? Anyone with knowledge knows the lock is in the middle of sash windows.

    Got 2 bathrooms one upstairs and one downstairs. Jacuzzi upstairs been switch off and used a normal bath. eho switch it on and of course a whole foul smell came up being unused for 7 years when i was living in it. eho required me to clean it as unhygienic? its not used as Jacuzzi. only as a bath and the bath hole is fine. lots more strange requirement.

    Was told to remove my 8 bikes and surfboard from front garden despite my living there. so where am i to put my bikes and surfboard? its for my kids and their friends when they visit me and i take them biking.

    where can i put my personal belonging with 4 lodgers in the house? i was also told to put away my boxes of stuff from the side of staircase where no access due to fire exit? there are no exit where the boxes are and certainly not accessible to lodgers . its a blank wall.

    Please can anyone help advise. Its too stressful and mind boggling.


  9. Water damage can be significant in causing damage to a property. Take precautions to safeguard your properties from retaining moisture which could eventually lead to mold. Good ventilation is key. Thanks so much for sharing!

  10. Thanks for this informative article, Tom. I suggest you send it to all the do-gooders in local authorities. One of the problems is the fact that these days so many legislators, housing officers etc etc know sod all about science and engineering. They come out of ‘uni’ with some soppy qualification in the arts, politics or media etc and literally cannot understand the difference between condensation and damp and just bleat on and on about tenants suffering and how it’s always the landlord’s fault.


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