It creeps across walls and ceilings, it hides behind furniture and clothes!

And no matter how much bleach you apply ‘The Thing’ keeps returning.

Often mistaken for penetrating or rising damp, condensation related mould is a problem in most Spanish houses, even new ones. As well as being unsightly, mould can aggravate and cause respiratory problems particularly in for elderly, young and asthmatics.

Diagnosis:- Identifying the cause of damp can be difficult, and may require use of a damp meter, but condensation related mould is typically green to black in colour and normally located at high level (e.g. wall /ceiling junctions) on the outer walls of bedrooms. Commonly it is also present behind beds and other furniture. Most penetrating damp issues don’t result in mould, so green / black patches or spots on outer walls are normally a sign of problems caused by water vapour from within the living space.

What Causes it?:- Unfortunately its you, the occupier (and probably your guests). Normal occupancy involves cooking, washing, bathing and breathing, all of which produce water vapour. This vapour remains airborne as a gas until it either leaves the property, (through ventilation) or finds a cold surface to condense. The surface dampness caused by condensation is normally just the right low level to encourage mould growth, which is triggered by generally present airborne spores.

In addition to vapour from living activities, the evaporation of other damp sources e.g. leaking water pipes, ground water etc will also aggravate the problem. Any house that has not been occupied for some time, but features recent mould growth may well have leaking pipes or rising damp.

External walls are generally colder especially where insulation or voids are not included e.g. solid wall / ceiling junctions, concrete lintels and ring beams, or simply corners (where insulation may not meet). Typically the problem will be most evident in these areas (especially if north facing), however moving furniture away from outer walls will often reveal sometimes quite shocking amounts of mould. The reason for this is that furniture (especially beds), restrict wall surface air flow and insulate the wall from convected and radiated heat. As the wall behind the furniture becomes much colder than the rest of the house,  condensation will result, the mould also happens to prefer less UV, so darker areas promote even more growth.

Which properties are most prone?:- Unfortunately newer properties can be more prone than say a 30 year old villa, because older properties tend to feature single glazing and draughty openings in general. Conventional open fires or wood burners encourage a constant circulation of air, when compared to modern balanced flue boilers. Single glazing also serves as a ‘sacrificial’ point, encouraging vapour out of the air. While double glazing may feature trickle vents, it’s human nature to close these at the very time when condensation is at it’s worst e.g. cold winter days and nights. While most new build properties now incorporate insulation, poor architectural detailing and on site practice inevitably result in numerous cold bridging points within the property, this combined with warm windows, sealed openings and modern heating, is likely to result in a more exaggerated problem.

NB:- Installation of gas, oil or solid fuel fires or wood burners, must be accompanied by increased ventilation in newer properties, to avoid the risk of suffocation in an over sealed room.

As water vapour increases so does the air pressure, as a result, vapour tends to travel easily through the property often causing mould in colder rooms, which can be a long way from the original vapour source, e.g. kitchen. Many new build property owners wrongly assume that water is penetrating from outside and sometimes end up taking builders to court for the wrong defect. While water ingress e.g. into the outer leaf of blocks, will encourage more cold bridging and hence more internal condensation, it is actually rare for external damp to penetrate the whole wall. As a result the court may order that the builder pays for repainting of a property when this will not solve the condensation problem.

How to get rid of it:- The most prone areas can ultimately be insulated from the inside e.g. through application of a glass fibre or polystyrene insulation, fixed with screwed treated timber battens and finished with a ‘vapour check’ membrane with skim coated plasterboard over. The vapour check must be included (and well sealed at edges) to prevent vapour from penetrating through the insulation to the cold wall surface. Other methods can be used including spray applied polyurethane foam (plastered over) or the formation of a cavity e.g. a 5cm lining of ceramic cellular blocks over cavity insulation (well butted to surround walls and ceiling).

‘Anti Moho’ sprays and paints can also be purchased. Ideally wash affected areas first, (e.g. with warm water and washing up liquid). Use of bleach is not necessary and does not work. Once dry, spray apply ‘Anti Moho’ treatment (ventilate well and use mask), leaving it on wall to dry properly (24 hrs), then paint with two coats of ‘Anti Moho’ paint. (a good paint shop can colour this for you).

Then follow these simple rules to reduce the problem:-

Increase ventilation and heating to all living areas.

Ensure that kitchens and bathrooms have good natural ventilation or install mechanical extractors. (Keep lids on pans. Putting cold water in bath before hot can significantly reduce steam). Open window and close door after use.

Make sure that your tumble drier discharges to external air.

Avoid use of gas bottle or paraffin heaters.

Open bedroom windows when you get up in the morning (ask guests to do the same).

If installing double glazing, make sure it features trickle vents.

If installing central heating locate radiators on external walls e.g. under windows.

Place dehumidifiers (chemical or mechanical) within the affected rooms.

Each damp source has a specific solution. Proper diagnosis of damp is an essential part of the elimination process.

If you have a building structure related question you can e-mail Mark for free initial advice :–   This email address is being protected from spambots. You need JavaScript enabled to view it. A free 16 page buyer’s guide is also available on request.

NB:- Information for advice purposes only. Proper legal and safety procedures should be followed for all property purchases and building works.

Information provided by Mark Paddon BSc Hons Building Surveying. ICIOB, property purchase advisor in the Valencia region.

T: 962807247  M: 653733066

ã Mark Paddon 2006

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