FREQUENTLY ASKED QUESTIONS

Unfortunately there is no simple solution because condensation in the home can be caused by various factors, not least the occupancy lifestyle. You can download from our Condensation page an Information Sheet giving various Do's and Dont's and tips on how to minimise condensation. Ventilation, heating and air circulation are the key issues. In high humidity areas, like the kitchen and bathroom, extractor fans will help but the most effective whole house solution is to install a positive pressure ventilation unit in the loft. This will circulate dry, relatively warm air quietly round the property and help to eliminate cold spots when condensation can form.

This sounds like a classic case of condensation - and nothing to do with the damp proof course injection years ago. The issue is likely of be one of inadequate heating levels and insufficent air circulation in the spaces concerned. The colder air becomes, the less able it is to retain moisture so when it meets a colder surface such as an outside wall, the moisture in the air condenses and this leads to dampness on the surface. If air circulation is poor, then this dampness and the stagnant air create the ideal condition for mould growth. The solutions include increase heating levels, improving air circulation and (particularly in the case of high humidity areas such as kitchens and bathrooms) extracting moist areas at the point of generation using an extractor fan. There is a customer information sheet on the web site which may help further. Peter Cox can supply a positive pressure ventilation system if required to assist in getting air circulation around the property but the first step is to come to tackle the basic issues mentioned above.

This scenario certainly sounds like condensation. Spare rooms are often susceptible because of lower heating levels, reduced ventilation and less air circulation. Under stairs cupboards are prone to condensation for similar reasons. You could test this by clearing off the black spot mould from the spare room wall with a proprietary fungicidal wash, increasing the heat and ventilation for a period and seeing if the dampness on the wall surface returns or not. There's a condensation information sheet on our web site which you may also find useful.

It is highly unlikely to be a rising damp problem because all modern houses like this are built with a damp proof course and the edge of this should be visible on the outside. In theory the dpc might have failed locally but again this is unlikely given the modern materials used. The more probable culprit is condensation particularly given that the wall has been lined with polystyrene. Mould growth is usually a tell tale sign of this. Bedrooms, especially spare rooms which are used irregularly, can be prone to condensation because of lower heating levels and air circulation. Polystyrene panels are more usually found on ceilings where they can help to prevent heat loss but on a wall they could just be serving to prevent any moisture in the masonry wall evaporating naturally. You might wish to consider removing a test panel and see if the damp persists.

This sounds like a classic condensation scenario and the presence of black mould confirms it. What is happening is that the relatively warm moisture laden air inside the building is meeting the colder surfaces of the outside walls. The lower the temperature the less moisture air is able to contain, so at the point where the temperature drops (known as the 'dew point'), moisture in the form of condensation will be released. And this provides the conditions for mould growth to develop. So yes, adding insulation to those outer walls shuld be beneficial because it will raise the surface temperature and reduce the likely of surface condensation forming. But as your question implies, air circulation (or lack of it) is also likely to be playing a part in the problem. An air brick will certainly introduce drier but colder external air but you might first wish to consider a way of increasing the circulation of the warmer air inside the room e.g. by cutting vents at the top and bottom of the wardrobe doors. This is suggested because with insulation and circulation, heating level is the third element to consider in eliminating condensation.

In such a restricted area, it is unlikely to be a problem of rising damp. If there is a dusting of white powder on the wall face, it could be a localised problem of hygroscopic salts in the masonry migrating to the surface and then the moisture evaporating to leave some salt deposits behind. But the greater likelihood is condensation, particularly if the problem is in a corner where air circulation is restricted. This can be monitored over the next few months. As ambient temperatures rise with the onset of summer, the dampness should disappear if it's condensation because warmer air can hold more moisture. When autumn returns and air temperatures fall, if the problem re-appears that will confirm the diagnosis.

It is a problem in that it indicates a high level of atmospheric moisture and an inadequate means of evacuating it, because black mould indicates a clear condensation problem. Condensation is often down to occupancy lifestyle just as much as building construction issues such as insulation standards, heating provision and air circulation/extraction facilities. For more information see the customer information sheet on our condensation page. Building standards in the 1930's did not focus on insulation in the same way as we do today so you would need to check what property improvements have since been made in this area, as an upgrade will be necessary to take account of modern 21st century lifestyles.

This appears to be a classic condensation problem. Levels of insulation, heating and air circulation are all critical factors behind the presence of condensation and it sounds as if this part of your property fails on all 3 counts.

So yes, a heater would help to raise air temperature and the higher the temperature, the more water vapour the air can hold without releasing it in the form of condensation. But see what you can also do to improve the insulation to the walls and ceiling in order to eliminate those cold spots where condensation will form. Thirdly can youÿincreaseÿthe airÿcirculation in the hallway - e.g. by adding vents at high and low level.

If none of these are feasible without much disruption, yes, aÿdehumidifier will be quite efficient inÿremoving any condensation that does form and help to alleviate matters in the short term. But it won't solve the problem of course.ÿ

It sounds like a classic case of condensation. (It's unlikely to be rising damp unless the dampness is distinctly restricted to the lower half of the wall)

What's probably happened is that by installing the wardrobe you have created an area with little of no air circulation and because the external wall is uninsulated and cold, moisture in the air is condensing on the wall whereas previously it might have been prevented from doing so by better ventilation.

And condensation creates the climate for mould growth.

Insulating and lining the external wall will certainly help but perhaps also you could add some ventilation holes top and bottom to the wardrobe doors. ÿ

It sounds as if you are confronted with a typical condensation problem. Certainly the vents you have installed will help because one of the reasons for the formation of condensation is lack of air circulation.

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The outside wall you refer to will probably be the coldest of the surfaces within the under stairs space so it will be here that any moisture vapour in the air will turn into condensation. This is probably largely hidden behind the panelling.

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If the wall is above ground level, then you could insulate and panel it fully ? this would eliminate the cold spot.

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However you mention a split floor level, so if part of the wall is below ground or damp proof course level, then you will need first to apply a waterproof render to the wall to create a barrier against lateral water penetration.

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Painting alone will be just cosmetic and won?t address the underlying issue.

The problem you have described is most likely to be one of condensation forming on the inside of the wall and this in turn is creating the conditions for black mould growth, a common symptom of this form of dampness.

The section of the wall which is wet will be that much colder, sufficient to mean that air inside the room will condense here whereas it won?t necessarily on the adjacent, relatively warmer, surfaces.

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You can wipe off black mould growth with a fungicidal wash but it will continue to return all the while this section of the wall remains damp.

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First and foremost you must repair the external downpipe leak. Stop this moisture source, then the wall will dry out over time and the conditions for condensation formation on the inside should disappear.

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The presence of black spot mould, particularly at the wall corners, indicates that this will be a condensation problem first and foremost. And a heavy incidence too. A failure in the dpc installation is much less likely.

The principal problem is most probably lack of air circulation at this point. (Wardrobes are similarly prone for the same reason). Unlessÿyou go to the trouble and expense of installing cavity wall insulation, the wallsÿare always going to be colder surfaces where warm moisture laden air from inside the homeÿwill cool rapidly andÿcondensation will result (because cold air cannotÿcarry as muchÿwater vapour as warm air). The resulting surface dampness then provides the ideal conditions for mould spores to thrive.

So after identifying any ways in which you could cut down on moisture generation at source - eg in bathing andÿcooking practices - measures you could take includeÿcuttingÿlocal ventilation slotsÿin the cupboards top and bottom, installing extractor fan(s) orÿforÿa whole house solution fitting a positive pressureÿventilation unit which will address the problem in all rooms of the house.ÿ

The musty smell certainly suggests condensation and even thought the interior face of the wallÿappears dry, there could be dampnessÿin the body of the wall.

Inevitably your description begs various questions and these would be in the mind of the specialist damp surveyor examining the property first hand. For instance what's theÿwall construction, are there anyÿexternal defects which might be causing water penetration,ÿand is the room north facing ?

The fact that the wall was originally lined out may not have beenÿto do just with its poor condition - there may well have beenÿhistoric condensation / insulation problems.

Allowing the wall to dry out and ensuring good ventilation in the room should solve the problem. Check the plaster though - if it sounds hollow, it willÿneed replacing (with a lime based render given the property's age). Otherwise you could renew the skim coat withÿa good bonding agent.

However it would be advisable to leave the work for as long as you can manage to allow any residual moisture to dry out before embarking on surface finishes. Meantime check the pointing and condition of the outside masonry, look at how to increase ventilationÿandÿrectify any other possible causes of moisture ingress.ÿ

Your own analysis appears to have identified the problem pretty well and if the condensation is forming specifically on the flues, then that in itself indicates that these must be the coldest surfaces in the room. You don't state whether the affected bedroomÿis used regularly but assuming it is, then theÿproblem is worse there because of the moisture being created at night.

As youÿhave highlighted, ventilation is probably the key so you should consider the installation of a positive input ventilation system which will create the necessary air ciculation without undue heat loss - in fact the heat would be re-circulated potentially and thereforeÿcould save money on the heating bill. You don't need to keep doors open with this system as air will circulate through gaps in the building's construction.

This sounds like aÿcondensation problem whichÿcan often be an issue in sub floors with inadequate natural ventilation.

Quite apart from the timbers getting damp, there is the much more serious risk of fungal decay (dry rot) breaking out. Dry rot spores which are in the atmosphere all the time only need timber moisture content of 20% to start germination - that's why dry rot often arises after floods where the sub floor timbers, having been saturated, are in the process of drying out and in doing soÿat some part in this process present the ideal conditions for dry rot to start.

The solution ? Check the vents in the outer walls and any inside cross walls to ensure a good, consistent flow of air. If necessary add more vents.ÿAlternatively if the constrcution makes this difficult, look at installing a mechanical air circulation unit of the type more usually fixed in a loft to combat internal condensation.

This is almost certainly a condensation problem and if so, a very typical scenario. The reason is that wardrobes get very little air circulation and if they're situated against an outside wall, that wall will be a colder surface which is likely to result inÿthe formation of condensation. And condensation frequently leads to mould growth. In all probability your clothing is at risk from the dampness as well.

The answer is to increase air flow in and around the wardrobes. Soÿleave the doors open more often or fitÿventilation panels. And keep the bedroom warmer if possible because warm air holds more moisture.

If the problem is really serious rather than a minor irritant, the best solution we can recommend would be to fit in the loft a positive input ventilation unit - which operates exactly as its name implies, by quietly pushing warm air from the loft round the property to eliminate cold spots and stop condensation (and mould growth) from forming.

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This has all the hallmarks of a serious condensation problem. Black mould is always a tell tale sign. Cleaning off with bleach is effective but it doesn't address the underlying problem or the conditions that gave rise to it in the first place.

Condensation is triggered by excess water vapour in the air, inadequate air circulation and insufficient ventilation. Heating and insulationÿlevels are also significant factors.

After years of experience Peter Cox now recommend the installation of a positive input ventilation unit, either loft mounted or installed in a central hallway of a flat, as the most effective mitigation measure, backed up if necessary by extract fans in the kitchen and bathroom where the creation of water vapour is most intense.

You haven't said what floor level we're talking about here. However granite being so dense a stone, it generally doesn't suffer from rising damp although moisture can work its way intoÿthe mortar beds. If the outside pointing appears sound, it is more likely to be a condensation issue, particularly as the problem is located in the corner on an outsideÿwall, always one of a room's cold spots. Still, moistÿair at this point will cause water vapour to condense as it touchesÿthe colder surfaces.

Heating and insulation levels plusÿmaintaining good air circulation will beÿkey to the solution of this problem so venting the blocked up chimney is a good move. As an alternative to a dehumidifierÿyou may wish to consider installing a positive input ventilation unit which is designed to draw inÿwarmer, conditioned air from outside and circulate it round the whole apartment.ÿÿ

This certainly has all the hallmarks of a serious condensation problem. You are right to try andÿventilate roomsÿbut this alone is clearly not enough. Yes, a dehumidifier may help locally in a specific room butÿthe problem you describeÿcallsÿfor a whole house solution and for this we would recommend theÿinstallation of a positive input ventilation unit, either loft mounted if you have a roof space or else wall mounted if it's a flatÿor apartment. This will push warm, dry air around the whole property and help to eliminate condensation.

It may be necessary, dependingÿupon the house design, to supplement this with extract fans in the high humidity bathroom and kitchen areas.

For more information download our condensation controlÿleaflet for homeowners.ÿÿ

The likelihood is that this is a problem of interstitial condensation. This can occur in areas of the house where atmospheric moisture is that much higher.

Tryÿliftingÿsome tiles and leaving the floor bare for a while - if it dries out, then it's a condensation problem. The solution is to find some way to increase ventilation and reduce humidity which will be the main contributory factor.

If it doesn't dry out, then this suggests possibly aÿfailure in the floor damp proof membrane and it would need some test excavation to try to see what's happening.

If you read other FAQ's under the condensation section, you'll get the clear message that the solution lies in a blend ofÿinsulation, heating and ventilation and some of the answers may help your understanding of the problem.

An air brick will help certainly but it may not be sufficient. Perhaps the best short term answer is to add heating to the bedroom and open windows whenever you can, particularly afterÿcooking or bathing.

The mould is an indication of continuing condensation. Bedrooms because they are generally cooler, and wardrobes because of restricted air circulation, are frequently blighted by condensation.

The replacement windows (presumably double glazed) and trickle vents you mention are all good measures to have taken, as will be the more even heating temperature proposed.

Yes, cavity wall insulation will definitely help because it will retain heat and reduce the incidence of cold spots on outside walls where condensation tends to form. But even so you'll still need to maintain good air circulation, so as a prior step you might also wish to consider installing a positive pressure ventilation unit which will draw in and circulate warm dry air around the house . The capital costs will be less than wall insulation and running costs are pretty low at approx 1.5p per day.

The cavity wall insulation will have helped to reduce heat loss and raise the surface temperature of the inner wall surfaces, but that alone is clearly insufficient to deal with the problem you have - condensation.

If you look at theÿanswers to other questions placed on this subject, you will see that condensation can only be tackled by a combination of measures involving heating, insulation and ventilation.

Your child's asthma is the key factor which leads us to recommend that ventilation and air circulation will be the most important element to focus upon. Installing a positive input ventilation unit, either in the loft if it's a house or for a flat in a central hallway, will result in warmer, drier air being circulated around the whole property. Not only will this help to mitigate condensation, it will also improve the air quality, a factor that is so important for those with breathing difficulties.

A vent at high level would probably help although it will have the disadvantage of letting in additionalÿcold air into an already unheated part of the property.

Alternatively you could fit a positive pressure ventilation unit which would have the benefit of boosting air circulation in the affected area and discouraging condensation from forming.

But as you sayÿtheÿmajor contributory factor is the probable lack of adequate insulation in theÿceiling.ÿA solution would to install an additional ceiling underneath and includeÿinsulation above it. However there will be a very real risk of interstitial condensation unless you ensure there is an effective vapour barrier.ÿSo youÿwould need to use foil backed plasterboard with properly sealed joints or an equivalent specification.

Clearly the corner in question is a cold spot (presumably it's on an outside wall), hence the formation of condensation there. The air vent you've installed probably doesn't have sufficient direct impactÿon this area so you need to find some other way of creating air circulation.

Alternativelyÿbetter insulationÿis required to raise the surfaceÿtemperature of the wall, but that will be difficult without disturbing the new tiling.

Because it's such a relatively restricted problem, some form of local dehumidification might be one answer - however a kitchen is not the ideal scenario because of the amount of water vapour that this room will create in any event. Nevertheless it might be worth a try.

Bedrooms are frequently prone to condensation, particularly if they are on an outside wall. Primarily the problem isÿthey have little or no air circulation and get little in the way of heating. The lifestyle of your tenants could also be a factor - eg showers, washing, clothes drying etc. If this creates high volumes of moisture but ventilation is minimal,ÿcondensation will be inevitable and this will manifest itself on the coldest wall surfaces - which could well be the bedroom wardrobe.

If not already fitted, look at installing extract fans in the kitchen and bathroom to evacuateÿhigh humidity at the point of generation or a positive ventilation unit which will gently and continuously circulate warm dry air round the property. See the details of these products on our web site.ÿ

The bedroom dampness is clearly condensation, so as you will see in the numerous other answers givenÿon this topic, the factors you need to look at are heating, insulation and ventilation.

The dampness downstairs might need site investigation. Depending on the property age.ÿit could be condensation again (most likely),ÿpossibly a localÿfailure of theÿdamp proof course or penetrating damp associated with the newly abutting conservatory.ÿ

The problem is clearly one of condensation so it's the atmospheric conditions inside the property you need to address, not the external renderÿunless it is cracked or otherwise allowing moisture ingress. For this age of house and brickwork construction a cement based render is quite acceptable. Lime renders are more appropriate for older property whcih have been built with that specification in the first place.

As to the condensation issue, Peter Cox is now recommending the installation of a positive input ventilation unit mounted in the loft. This will move drier, warmer air around the property and reduce the incidence of cold spots where condensation can form. Temperature, ventilation and insulation are the key factors as answers to other similar questions on this site will confirm.ÿ

Without a survey of the property one can only speculate. However the dampness you refer to, especially in the bedroom, is likely to be condensation and this often manifests itself inÿmould growth. Condensation means a heightened level of humidity and this allied to the probable presence of mould spores means the quality of the air within the property will be impaired.ÿSo those occupants with asthma and similar susceptibilities will be adversely affected.

What do you do? The aim should be to improve the indoor air quality by addressing the three factors whichÿlie behind condensation - heating, insulation and, perhaps most important of all, ventilation. The installation of a positive input ventilation system which continuouslyÿpushes dry and relatively warm air gently around the property is the solution Peter Cox are recommending now. More details can be found on our web site.