Damp - Condensation

Mould on first floor bay wall?

Q We have a 1930's house with bay window to the front bedroom. The bay suffers with extreme condensation but this is only in the upstairs bedroom. The bay window in the downstairs lounge is fine? What is going on?

A Difficult to be specific without actually seeing the construction but very often first floor bay windows in 1930s houses are only one brick thick to save weight thus they will have a lower internal surface temperature making condensation more likely to occur. Ground floor bay windows will have 9" thick brickwork and the room is likely to be better heated than the bedroom. You need to insulate the first floor bay brickwork. Insulated plasterboard is one option or look at Mould Growth Consultants web site as they have a product called Sempatap (or similar I think) that may be suitable. You should of course stop all excess water vapour generating activities in the house especially internal clothes drying regardless of which room you do it in! It makes little difference.


Mould on wall behind washing machine

Q I have a mid terrace house dating from 1880.  I seem to have damp all over the wall with the sink on it.  I have looked and I do not have a leak.  I believe this wall is a lime mortar with no damp proof cause. The lay out of the house is lounge to dining room, to kitchen where problem is and then the bathroom. This is the only wall with problems though. The bathroom was an extension and has a dry line installed. I am just looking for some advice. The wall backs onto the courtyard and has a concrete floor up to the wall. Would this cause a problem? I am just wondering if there is a way I can ventilate the wall better without going down the route of expensive injection damp proofing. I look forward to hearing from you.

A You say 'damp all over the wall'. How is this showing itself - what are you seeing? Is it just dark and wet to touch or is there black mould growth present. Is it above and below the sink level? Does it creep out onto the ceiling? Is it a single storey extension if so is the roof above insulated? The concrete floor is very unlikely to be the cause. Let me have more information and I may be able to be of more assistance.

Q Thanks for getting back to me. The damp is not all over the wall only under the sink and behind the washing machine.  I have a radiator on the right hand side so no damp there. The plaster is ok but the wall is covered in a black mould that can be wiped off and smells of damp. It is only dark and wet to touch. Touching it would make my hand go black. It is all below the sink. None present above work top. The kitchen has my spare room above it. My house a 2 up 2 down mid terrace with the kitchen and bathroom on the ground floor. This is the only wall showing damp. This is also the only wall without a damp course on it that is exposed. Hope this helps more. Thanks.

A From what you describe and where it is present condensation is likely to be the cause. Very often when condensation is a problem in a property mould growth is very common behind washing machines and kitchen base units. You do not get mould growth on walls if water from the ground (rising damp) is present. Damp (water) does not smell - what you are smelling is mould - a musty smell. Do not waste your money on injection DPC. You should look at insulating the wall surface where this is happening. Please read the information on this site about condensation.

Q Hello Peter
Thanks for this.  You say insulating the wall?  How do I go about doing this?  Is this something I can do or do I need to get someone in?  If so how much? Thanks for your help with this. Appreciate it.

A Have a look at Mould Growth Consultants web site http://www.mgcltd.co.uk/ They have a product called Sempatap which could be OK for what you want. Failing that look at gluing insulated plasterboard to the wall surface.


Mould and rusty nail head in bungalow bedroom

Q In the 2nd bedroom of a bungalow there was black mould on the wallpaper and a rusty wet nail in the skirting board on the outside wall. On removing the paper the plaster was dry with no sign of damp or mould. Could you suggest what has happened to the skirting board please? I

A From what you describe it sounds very much like condensation is the cause of your problem. Mould will normally only grow on a wall where there is a pure water source such as rain water, tap water or condensation. It will not grow on surfaces where the water has originated from the ground - such as rising damp as this contains salts and minerals which act as a 'mouldicide'.

Bungalows are notorious for suffering the effects of condensation. Spare bedrooms can suffer badly - especially those with north walls. Condensation is caused by lifestyle - what you do in the property - and probably the single biggest contributor is drying clothes internally on and against radiators. The condensation season is November to March and very probably during the summer you will not experience a problem. The rusty nail head is likely to be due to condensation forming on it since it will be colder than the surrounding wood.

Look at everything that you do that produces water vapour - cooking, washing, clothes drying etc. and extract as much as possible directly to the outside at source. Insulate the property well especially cavity walls. If you insulate the walls the inner skin of brickwork will be warmer and therefore less prone to the effects of condensation



Damp and green mould - I'm very worried

Q I have damp all upstairs on my ceiling and it has always been in the bathrooms but have noticed it's got much worse since we have the heating on. I'm really worried that the longer I leave it the worse it will get. Also I have pine furniture throughout my house and have noticed that I get green mould on the side or back. It's wiped off but will return this is upstairs and only in the front room. I don't know really where to go to get this fixed as I don't want to be told a lie and get someone in then for it not to be sorted. Please hope you have an answer as I'm very worried.

A What you describe sounds like a very bad condensation problem. If you read the condensation pages on this web site you will realise condensation is the result of how we live in our houses i.e. our water vapour generating activities combined with the amount of heat we use. Do you dry clothes inside? If so stop this immediately as it is the biggest contributor to water vapour levels in a property. Are all areas adequately heated? Is the roof adequately insulated? Read our web site about condensation myths and you might want to consider buying a domestic dehumidifier.


Mould on wall, floor & shoes

Q My bedroom window gets a lot of condensation on it even though it is double glazed. I don't usually have any heating on in the bedroom (I have electric storage heating) and by the morning the windows are running with water. Over the last couple of months a black mould has started to appear about half way up the back wall which backs on to the stairwell up to my flat as well as the wall under the window. I have to clean it every day. If I leave it for more than one day anything that is on the floor also gets mould growing on it,even my shoes. What can I do to stop and cure it?

A What you describe is almost certainly condensation and it is what is referred to as the life style of the occupants of your property that is causing/generating the water vapour that eventually forms as condensation resulting in mould. Why is the heating off in the bedroom? Leaving it on will help as warm air is able to support more water vapour so less will be deposited on the window/walls/clothes. Do you dry your clothes inside? If you do then stop this immediately as this is probably the main cause. Do you have extractors in the kitchen and bathroom? Are they working? You should also consider purchasing a domestic dehumidifier and run this when the air is warm with all of the windows closed. Are our questions striking a chord? Are we on the right trail? Read the condensation section of this site and Article 1 to help you understand what is happening

Mould in wardrobe

Q My daughter's 1950's semi detached house has a built in wardrobe that incorporates two outside walls. There is no 'lining' of the wardrobe - the outside walls of the house are the back and side of it. The clothes in the wardrobe feel slightly damp and there is a small patch of black mould in the bottom corner. I am thinking of insulating the wardrobe by using something like polystyrene sheet of the type used for concrete floors and then facing this with plywood. I'm also thinking of combining this with the installation of an air brick into the inner leaf of the cavity wall, in the area where the mould is, to improve ventilation. Any advice on this proposed approach would be appreciated.

A What you describe sound very much like a condensation problem. Rather than use polystyrene and ply we would suggest that you use insulated plasterboard that incorporates a vapour check on the warm side. A vapour check is very important otherwise condensation could form on the cold wall behind the insulation. This may be cut to size and glued up using 'no more nails' or similar. A vapour check is very important and the proposed method you described did not appear to have one. I would not bother with the air vent as the insulation would make this unnecessary.


Walls black - clothes green!

Q I have been living in a flat roof property for 6 months. I have redecorated the property but in my daughters room the walls are turning black with damp. The bed has been moved to the middle of the room because of this and also the bedding was getting wet if it was against the wall. I have also had to take the chest of drawers out of the room as the clothes inside had green mould on them. This also happened with the clothes in the wardrobe. The houses have been noted for being damp in the past. My daughter's room has an air vent also the window is always on the latch. The property has an airflow system fitted. I have been told by the housing association that it is condensation in my daughter's room. I disagree with this, could I be right? I also have damp in my bedroom as the roof is leaking

A I know that this is not what you want to hear but everything you describe sounds like condensation is the cause. The amount of moisture/water vapour released into the atmosphere from a localised leaking roof is negligible when compared with one breath of a person. The winter months are the worst for condensation which is the period you have been living there. During the summer the problem will disappear but unless things change it will all return next winter.

Poorly insulated and inadequately heated properties will be more prone to the effects of condensation. It is likely that the flat roof is not well insulated and if the external walls are solid then insulation options are significantly reduced. If you have read about condensation on our web site you will have realised that condensation is the result of the life style of a property's occupants - it is not caused by the property. It is also acknowledged that some properties are more prone to condensation than others, flat roofed properties being amongst them.

You need to look very carefully at all the activities you do in your property that produce water vapour:

Breathing - not a lot we can do about this!

If you dry clothes anywhere inside the property this should stop immediately - this is one of the worst causes of condensation.

Adequate powered extractors should be fitted and used in the kitchen and bathroom and both areas used with the doors closed.

Constant dry heat should be used in all areas - not just short sharp bursts.

Does any excessive cooking or washing take place in the property?

Are tropical fish tanks present?

You may also want to consider running a domestic dehumidifier. They are not expensive to run - like a fridge - and very effective.

Hope the above is of some assistance to you.


Who is liable for decoration costs?

Q Who is liable to pay to repair and redecorate after damage due to mould of condensation dampness, landlord or tenant?

A The answer to your question is 'it depends'. If the landlord has failed to provide sufficient permanent ventilation and adequate powered extraction in the kitchen and bathroom then it is possible that a case could be made against the landlord.

If on the other hand the lifestyle of you and the other occupants in the house is such that excessive water vapour is generated resulting in condensation and mould growth then this would very likely be down to you. You should seek a legal opinion. Have you tried using a domestic dehumidifier to reduce the levels of condensation?


Bungalow with condensation

Q We live in a semi detached bungalow and have black speckled mould on our bedroom wall which is actually the outside wall.  There are fitted wardrobes against this and the mould has also appeared inside on clothes, shoes etc.  A couple of questions, firstly what should we do?  And secondly is it harmful for us (particularly as we sleep in this bedroom)

A What you describe are classic symptoms of condensation in a bungalow, particularly with fitted cupboards against outside walls. There is a great deal of information on this web site about condensation, a whole collection of questions and answers and an in-depth article about it under 'Informative Articles' (Article 1). The mould should not pose a problem since there are probably more spores outside than inside - even with mould on walls. Be careful however as there are a lot of 'mould is gold' contractors starting up in the UK. If you dry clothes anywhere inside the property this should stop immediately. Where you dry them makes no difference as water vapour will quickly distribute itself uniformally throughout the property. There should be powered extraction in the kitchen and bathroom. The walls and ceiling should be adequately insulated and the heating used constantly as a background heat - not in spurts morning and evening. You may also want to consider buying a domestic dehumidifier which is cheap to buy and run. Am I making any sense with what happens in your home?


Condensation forms on a pipe

Q Having recently purchased the ground floor flat in a 100 year old mid terrace property we repainted the bathroom including the ceiling around 3 months ago. We noticed water on the floor next to the old iron toilet after a couple of weeks, adjacent to the old toilet is an old pipe which does not serve our flat but we believe supplies the mains water to the upstairs apartment. Over time we have noticed some form of condensation on the pipe and black mould in areas up the pipe. At the ceiling level there is also a stain of what we believe is water surrounding in the pipe where is penetrates the ceiling, the stain is a perfect circle. We reported what we believed to be a leaking pipe to the owners of the upstairs flat but their plumber could find no sign of a leak. Could this merely be condensation and is there anything we can do about it? There is evidence where the pipe runs close to the wall at ground floor level that the wall is becoming damp, we have recently had the damp works done to the other side of this wall. Any ideas? Thanks!

A What you describe sounds like condensation forming on an incoming rising main which is common since it contains cold water. It will also form on the pipe in the ceiling void above and run down the pipe until it hits the plaster and will eventually show as the water ring you describe. The solution is to re-route the pipe or lag it with an insulation that has a foil outer covering to prevent water vapour reaching the cool surface of the pipe under the insulation. I know this is all easier said than done so good luck!


Damp upstairs - Condensation - What to do?

Q I have damp all upstairs on my ceiling and it has always been in the bathroom but have noticed it's got much worse since we have the heating on. I'm really worried that the longer I leave it the worse it will get. Also I have pine furniture throughout my house and have noticed that I get green mould on the side or back. It's wiped off but will return this is upstairs and only in the front room. I don't know really where to go to get this fixed as I don't want to be told a lie and get someone in then for it not to be sorted. Please hope you have an answer as I'm very worried.

A What you describe sounds like a bad condensation problem. Warm air rises and is able to support a greater amount of water vapour hence the problem becomes worse with the heating on. The water vapour supported in the air has to be generated somewhere and if you read this web site you will realise condensation is the result of how we live in our houses i.e. our water vapour generating activities combined with the amount of heat we use. Do you dry clothes inside? If so stop this immediately as it is a major contributor to water vapour levels in a property. Are all areas adequately heated? Is the roof adequately insulated? Read about condensation myths on this web site about which might help you understand what is happening and you might want to consider buying a domestic dehumidifier.


Is it rising damp or condensation?

Q We recently brought our first house and were told after our initial survey to have a "Damp and Timber Expert Survey" carried out. This was arranged (free of charge) by the estate agents managing the sale. I have read many of your FAQs and understand the pitfalls of DPC's; they say we need one on our 1920s terrace house, even though there are no visible signs of damp. I understand that doesn't mean there isn't but surely condensation can be misdiagnosed as rising damp? Our under stairs cupboard smells very musty, is that a sign of condensation or rising damp? (Or both!?!). The lowest bricks visible outside our house have a white salt (sulphates?) deposited on them, which stops at a dark layer of bricks that runs all the way round the house- is this the existing DPC?
And lastly, since damp meters are calibrated to use on timber, how can they be used on brick?? I understand calibrations, as I calibrate many types of moisture meters at my place of work, but none of them use resistance. Surely the composition of brick and timber are different enough to render them useless, especially if they are used on wall paper in a house with a condensation problem?

A Condensation is very often mistaken for rising damp which is why, especially during the winter months, a condensation check should also be undertaken as part of a damp investigation even though it is a photograph in time. Unfortunately not many do this or even know how to do it and most do not even possess the equipment necessary! To do this one needs to measure the air temperature and relative humidity to establish the dew point temperature (the temperature at which condensation will form). Wall surface temperature readings should then be taken to see where they are in relation to the dew point temperature.

The musty smell in your under stairs cupboard could just be a sub floor musty smell percolating up through gaps between the floorboard (assuming you have a timber floor). Condensation is unlikely on a party wall. Check the sub floor void and you may need to improve the subfloor ventilation.

The darker course of bricks could well be the damp course. If they are dark grey with a slight metallic finish they are engineering bricks and these were used as a DPC.

One can use a moisture meter calibrated for wood on any surface one wishes but the readings obtained from surfaces other than wood are only qualitive and not quantitive. When used on masonry, plaster etc. the readings obtained are only a guide. The pattern of readings obtained is important as is the skill, knowledge and experience of the user! They are very sensitive when used on masonry and this point is sometimes exploited by companies offering so called 'free' speculative surveys. This is why I would always advocate engaging an independent surveyor such as myself - but then of course I would say that!!. Granted this service will cost you money but more often than not is saves money by preventing unnecessary work.


New build condensation

Q I moved in to a new build bungalow and have a lot of problems with damp and mould. The dark mould started at the skirting board level and rose about a foot in the bedroom and lounge. On one external wall the paint work has become spotted, as if sprayed with water. Also Green mould had been on the back of furniture on external walls. I have now pulled this furniture out from the wall providing an air gap between them. I have a trickle extractor fan in the bathroom and kitchen, which are on all the time. I only dry clothes in the bathroom. I have cleaned up the mould with Milton and have been using a de-humidifier. This did help temporarily. However I have been suffering badly with breathing difficulties and dizziness. I have been told that new builds have damp problems and always contain a lot of water and this problem is normal. Am I being fobbed off or is this true?

A It is not unusual for new build properties to suffer from condensation and mould whilst the many hundreds of gallons of water used in construction evaporates off.
You should not dry your clothes inside irrespective of which room you do it in. You might as well dry them in the middle of your lounge instead of your bathroom as the water vapour produced by drying clothes inside very quickly distributes itself throughout your property. We suggest that you run your dehumidifier all of the time especially when the air in the property is warm as this is when they are most efficient. This time next year there should be a considerable improvement. If you feel unwell then you should seek medical advice.


Polythene and insulation - now I have condensation?

Q Have insulated a single skin wall with polythene, battens, insulation and plasterboard and have noticed a lot of condensation since the cold weather. What is the remedy for this and what do you think is causing the problem?

A You do not say where you have noticed the condensation? Polythene is a vapour check material so if you have covered all or most of the external walls through which water vapour used to escape then your action is likely to cause a problem. It's like living inside a large plastic bag. Which side of the insulation the polythene is could also cause problems. It should on be the warm side (room side) of the insulation not against the wall. If you have fixed it the other way around you will probably experience bad condensation on the polythene behind the insulation which could even trickle down onto the floor. You could try fitting a vapour check on the room side of the insulation but have you fixed plasterboard? You also need to let the vapour out so open windows/install a vent otherwise use a dehumidifier. Hope this helps.


Wall rendered now bedroom has mould?

Q We have an old Victorian terrace circa 1890's and have had the front of the house rendered. Since then we have had a lot of problems in the front bedroom with mould on the walls and damp smells. Someone advised us that the walls are wet and they are drying inside as the front of the house was rendered. There are no ventilation bricks at the front either. Would re-rendering the bedroom walls sort this or do we need to take of the rendering and allow the walls to dry out?

A Think very carefully if anything else different such as new windows, clothes drying inside, new dog, additional resident, different heating times etc. has changed inside the house since the front was rendered. If not then a possible answer is that the render, and may be the paint covering, applied to the front elevation is restricting the passage of water vapour that originally passed out through the wall with relative ease. Whilst it is possible it is doubtful that the wall is wet - why should it be? Have this checked by someone with a moisture metre and what are called 'deep wall probes' which enable inside the wall to be checked via drilled holes. Everything else being OK then it sounds like condensation and it probably will not be a problem during the warmer summer months. You could install what are called trickle vents or perhaps run a dehumidifier but look at all of your water vapour generating activities and extract at source or stop them.


How is interstitial condensation prevented?

Q Can you describe me please how interstitial condensation is to be prevented within the external walls and roof construction? Without any necessary calculations.

A To prevent interstitial condensation one needs to install vapour checks (vapour proof material) in the correct position to stop water vapour from entering the fabric in which interstitial condensation might occur. Please read article 'Condensation 12' under 'Condensation Explained' on this site which lists the vapour resistivity of some common building materials. Within a pitched roof condensation tends to form on the underside of roofing felt beneath the roof covering but I would tend to consider this to be surface condensation as a result of inadequate ventilation or incorrect construction (see Picture Gallery - Condensation - on this site for a picture of this). I consider interstitial condensation to be that which forms within a material, usually due to a declining temperature gradient, i.e. in the middle of a solid brick wall.


Damp in parents bungalow

Q I really hope that you have some advice regarding damp in my parent's bungalow. My parents are quite elderly; their bungalow was built in the 1960s and has always suffered from damp and a form of grey mould mainly in the corners on the external walls.  Is this rising damp and could this be from a damp course that has now stopped working?  They have tried everything from cavity wall insulation, special paint and lining the walls with polystyrene sheets but it is still present. Should they have a new damp course fitted or will this not make any difference?

A It is very unlikely that the damp proof course has failed in a 1960 property. Bungalows tend to be more susceptible to condensation during the cooler winter months and effective insulation combined with an adequate consistent dry form of heat is essential to reduce the likelihood of condensation forming. It cost a great deal of money to provide adequate heat throughout a property and very often the bedrooms suffer the worse effects of condensation as they tend not to be heated to the same extent as other areas. Elderly people on fixed limited income tend to heat the living room but the other areas are sporadically heated which might warm the air for a short time but not the fabric of the property. Naturally lifestyle of the occupants should be looked at and all water vapour generating activities such as clothes drying, cooking, washing etc. should be assessed to see if the water vapour may be extracted at source or stopped. It is appreciated that we all have to live and you may wish to consider installing a domestic dehumidifier to run during the winter months.


Son's house getting more damp after foam insulation?

Q My son's house has become gradually damper over the last few years, and they now use a dehumidifier which removes litres of water a day. They have noticed that when they had the cavity wall insulation installed, which was a few years ago, 2 of the air bricks are now blocked with the foam. Is this likely to be a cause of the damp? They also had the underside of the roof sealed with solid foam - could this be in any way a factor?

A The cavity wall insulation (are you sure it was foam?), blocked air vents and foamed roof are all likely to have reduced the vapour permeability of the building. This is the ability of the building to allow the natural movement of water vapour from and area of high vapour pressure (inside) to an area of lower vapour pressure (outside). It is possible that your son's life style may also have changed such as additional children, dogs etc. which may be a contributory factor. Obviously the blocked air vents should be cleared out and it is also very important to extract all water vapour generated inside at source i.e. extractors in the kitchen and bathroom and NEVER dry clothes inside. Consider installing some trickle ventilators.


Is it condensation?

Q In my downstairs cloakroom the floor at the back becomes damp. Do you think this is condensation and how can I establish if it is or not?

A Impossible for me to say without seeing the situation and with the limited information provided. Condensation tends to be a winter problem so if it is not present in the summer months then condensation seems likely.  Condensation will also form on the toilet cistern and cold water pipes and drip onto the floor - have you checked this? Condensation will support mould growth whereas rising damp does not.

Council say I am liable for the condensation

Q I am a council tenant who has condensation really bad where it is ruining my clothes and furniture in the bedroom. The council say I am liable for this. Is this true?

A The moisture that forms as condensation ruining your clothes and furniture causing mould to grow has been produced by the life style of the occupants in your house. The house has not produced it. It is what you do in your house that produces water vapour which eventually ends up as condensation and the worst culprit is drying clothes inside. Do you do this? If you do stop this immediately. Effective insulation combined with a constant form of dry heat will help cut down the amount of condensation that forms which the council may be able to improve but look at everything the occupants of your house do that generates water vapour and try to reduce it. If all else fails a domestic dehumidifier will help.

Wow! What a great question!!

Q It's a little bit more complex. We have a blow down tank/vessel at the plant where I work. The tank is used to collect steam from different drains & condense it by introducing water inside the tank. The inside water showering is controlled by the temperature. Due to low capacity the full steam is not condensed & vented to atmosphere. Now we are doing a modification & will relocate the water line above all the steam inlets with a pipe distributor nozzle ring. Now in new position the water showering will cover the area above the steam & will develop a water mist above the steam. It is supposed that more condensation will occur in this way. I have two concerns, first is that excessive condensation will cause a vacuum & the tank is not designed for external pressure, the second is that if excessive steam is accumulated inside under the water mist then it will not find any space to vent... what may happen?

A Thank you for your question. A really fantastic question!

Unfortunately what you are asking is beyond the scope of our knowledge which is primarily to do with residential properties.


Mould! Smell! Help!

Q We own a split level, detached bungalow that is 30 years old.  We have double glazed upvc windows installed. We have a problem with the ceilings in the bedrooms of the house in that black spots and marks are starting to appear which are quite unsightly. We installed fitted wardrobes four years ago and have started to notice that clothes that have not been worn for a while have mould patches on them and reek of damp. There is no evidence of damp in the basement area, office area or garage, all of which are situated on the lower level of the property.  Is it possible it is something we are not doing properly that is causing this problem? Clothes are never dried indoors as we have an outside boiler house that dries clothes more than adequately in the winter months. Windows are opened to air rooms every day regardless of weather conditions. The property is surrounded by lliandi trees which cannot be removed by us as they are not on our land. Any suggestions are appreciated.

A The symptoms that you describe are typical of those encountered when condensation is the problem.  It is not unusual to get black spot mould on the ceilings, especially along the outside wall edge, which could be indicative of either no or inadequate insulation being present above. You should be able to check this. Fitted wardrobes against outside walls in bungalows are notorious for suffering the effects of condensation causing mould to grow on clothes, shoes and handbags.  We note your comment regarding the basement/office/garage, however it is anticipated that most of the water vapour within the property will be suspended within the warmer atmosphere of the accommodation areas above since warm air rises.

This having been said, some properties are more susceptible to condensation than others. There are certain immediate things that you should do: 1) Look at all the water vapour generating activities that take place in the house and wherever possible try and extract the water vapour at source with extractor fans. 2) Check the amount of insulation in the loft and if the external cavity walls have not been insulated then seriously consider having this done. This will have the effect of warming the inner skin of brickwork, making it less susceptible to condensation as well as maintaining a warmer atmosphere which is able to support a greater volume of water vapour. 3) You may also want to consider a domestic de-humidifier. These are relatively cheap to purchase and run. They should be run when the rooms are warm and all windows closed. 4) You may want to reconsider your habit of opening the windows every day regardless of weather conditions. Whilst ventilation is important, excessive ventilation could have the effect of chilling the fabric and contents of the property, leaving it more susceptible to the effects of condensation. Finally, you should look at how you heat the property, especially during the cooler winter months.  The whole property should be heated, including unused bedrooms, otherwise cold spots will be created and condensation more likely to form.


We hope the above is of assistance to you and please let us know if any of the points mentioned are relevant to your circumstances.


Mould around windows?

Q We live in a brick built end terraced house approx 60 yrs old and have black mould around most of the external doors and windows. We had upvc fitted 5 yrs ago, the brick air vents were filled in and every winter it comes back with a vengeance! Please could you give us some advice?

A It is assumed that you have checked that rainwater is not responsible. What you describe sounds like a condensation problem caused by a cold bridge at the window and door openings. Obviously you should look at all of the water vapour generating activities that go on in the house and if not already present consider extractors in the kitchen and bathroom and stop immediately any clothes drying that happens inside the property - this is probably the single biggest cause of condensation and mould. You may also want to look at Mould Growth Consultants web site and in particular a product they do called
Sempatap Thermal which you may want to consider using to line your window and door reveals if it is appropriate.


Should I insulate my walls?

Q I live in a 1930's semi-detached property and I am considering having cavity wall insulation, mainly to solve a small condensation problem in one of the bedrooms. However, I have read some disturbing reports of the problems this can cause i.e. condensation, water penetration, wall-tie corrosion etc. Would I be better to remove the original plaster on the affected walls and replace it with insulated plaster board?

A Whilst there have been some problems with some forms of cavity wall insulation generally there is not a problem provided you go for a good name. Whatever you decide there is no need to remove the wall plaster internally. You could glue insulated plasterboard directly over existing surfaces or you may want to look at Mould Growth Consultants and a product they have called Sempatap for applying to walls. Try addressing the cause of the condensation as well such as stop drying clothes inside and provide a constant form of back ground heat especially in unused bedrooms.


Mould on skirting in brand new house?

Q What would cause green mould on the skirting board in a brand new house and how can I prevent it from recurring?

A New properties always tend to suffer from excessive condensation problems during the first twelve months or so after occupation as the considerable amount of water used in construction and still present in some of the building materials evaporates off. It is possible therefore that this may be the cause of your problem which is unlikely to occur once the construction moisture in the building has 'dried'.


Condensation on door frame

Q I just installed a new garden door in my house, where the old sliding door was. In the basement I have a gas stove that I use to heat the basement. Now the problem is that when the gas stove is on then I get a lot of condensation on the metal frame of the door and it is getting on the living room floor.
A You do not state the type of gas stove you have but if it is a portable gas heater then we are not surprised that you are getting condensation as this type of heater produces vast quantities of water vapour as a product of combustion. All gas combustion produces water vapour and other bad gasses so you need to make certain that the area in question is adequately ventilated when the heater is on and we would recommend that you install a Carbon Monoxide detector - it could save your life. Metal door and window frames tend to suffer from condensation even if no where else does since they conduct heat/cold very well. Some actually have a thermal break in built to help reduce this.

Condensation and radiator positions

Q I have read your articles on condensation with great interest. Especially as I also have (allegedly) a similar problem that has haunted my family and me for the past whole year. Despite getting a damp specialist in who dismissed the problem as condensation without any cure, I am left confused and helpless in how this problem can be solved if it really is condensation.
I note from your articles that condensation is normally found between October - March months, but I seem to have all year round. May be it is due to the fact that our central heating radiators are not positioned underneath the window but on the opposite wall away from the window. And the condensation being on the window wall may be due to the lack of heat on these walls? Another concern I have for my family is that we have 2 very young children and I have been informed that the mould that grows as a result of this problem can cause respiratory illness especially as sleeping beds are close to the window wall and there isn't much of space to move them elsewhere. And this apparent condensation/dampness is not getting any better since last evening I saw some mould now growing into our living room wall.

I would most appreciate if someone could kindly contact me to advise what my best options might be to treat this problem that has left me becoming more and more worried for my family's health.

A The position of your radiators would have a slight effect but condensation tends to form on external walls since these are usually the coldest. If you have read the articles on this web site you will realise that the moisture that forms as condensation is caused and generated by the activities of the occupants.

You should look at how you and your family live - Do you dry clothes inside? Do you cook often and produce large quantities of steam? Does the kitchen have a powered extractor? Does the bathroom have a powered extractor? What is the ventilation situation in the whole property? Is the house heated adequately and constantly? Is the property well insulated?

Drying clothes inside is the worst contributor to a condensation problem - if this practice goes on stop it now! It is impossible to stop producing water vapour and some properties are without doubt more susceptible to condensation than others which may be your situation. You might want to consider purchasing a domestic dehumidifier which are sold at stores like Currys and Comet. A dehumidifier will help to control water vapour levels in a property and cost less than a fridge to run but always remember that it is the occupants who generate the water vapour in the first place.

Contact Peter: Email - info@dampdecay.co.uk - Telephone: 015242 71794