A survey in which the chartered surveyor had wrongly diagnosed the condensation and penetrating dampness as 'rising damp' and had unfortunatey missed the dry-rot under the dining room floor 

Property: Slaithwaite, Huddersfield

This is a good example of a valuation survey pointing a client in the wrong direction.  The chartered surveyor jumped to the wrong conclusins when he took his moisture meter readings and diagnosed 'rising damp'.  Fortunately for the client, she decided to take further advice before she instructed a contractor, who would almost certainly have agreed with the surveyor and proceeded to inject the property.  Whether or not he would have spotted the dry-rot is a debatable.  He would probably have confined his 'survey' to the areas indicated in the valuation report; as such he would have missed it too!

Instructions Instructions received by telephone to inspect the property generally for damp and timber issues.

Background The client is in the process of purchasing the property and her bank/building society has asked for confirmation regarding any timber and damp issues. In particular the valuation surveyor found damp in the front and rear walls of the property, which he attributed to ‘rising damp’. No other issues were highlighted.

Disclosures I have no affiliation, financial or otherwise, with the client or the property.

Limitations None.

Restrictions The survey was non invasive and non destructive. Access to first floor and the sub floor at ground level was restricted by carpets and furniture etc.

Date of Survey October 2004.

Weather Fine and clear.

Type of Property Stone built, inner through terraced house. Approximate age of construction 80 - 90 years old. No central heating but PVCu double-glazing is installed throughout.

External Observations The house has stone elevations to front and rear with the front elevation facing almost due south. The walls are nominally 350 - 400mm thick and have a stone outer and brick inner cavity construction on stone plinth. There is no sign of a damp proof course (dpc). The blue slate roof, viewed from ground level, appears to be in sound condition and the flashings appear adequate.

The front of the property has an entrance above carriage way level with a small hard surfaced garden to the front. To the rear the ground level is below the floor level of the property. In the front garden a small planting bed has been formed abutting the wall. One airbrick was visible but partially obscured by a planting box. At the rear are three airbricks. Two ventilate the cavity and one ventilates the sub floor. The two airbricks ventilating the cavity have been installed recently, probably to assist with ventilation when the double-glazing was installed.

Internal Observations General: The property is in good condition throughout and has gas fires in the front and rear downstairs rooms. These supply the primary source of heating although there is also an electric convector heater in the front entrance hall.

Damp : Inspection of the entire property showed no visible signs of damp.

Moisture meter readings were taken throughout the property with a Protimeter MMS plus. All skirting boards and walls gave acceptable levels except for the two walls previously referred to, i.e. in the living room and the dining room.

Living room: An area of the front wall gave above normal meter readings. This area extended from the extreme right hand front corner of the living room (viewed from the inside) for a distance of approximately 1700mm (5’ 7") to the left. In the right hand corner, where there is a small triangular timber shelf, it has attained a height of 700mm (2’ 3") and it tapers to nothing at its left hand side. The dividing wall between the living room and the entrance hall gave normal moisture meter readings.

Moisture meter readings taken in the skirting board in the area corresponding to the high readings in the wall showed slightly raised moisture levels but these were not sufficient to place them at risk of rot (16.6 – 17.8% Moisture Content).

A wallpaper sample in the area in question was taken and tested for salt contamination. The samples tested positive for both chlorides and nitrates.

All other areas of this room showed normal levels of moisture content in the walls and skirting boards.

Dining Room: High moisture meter readings were obtained all along the rear wall of the property. These readings were present at both skirting level and intermittently upto a height of 1800mm (6’). A plaster sample was taken and tested for hygroscopic salt contamination. This sample proved negative for nitrates but showed a trace of chlorides.

Timber: Timbers were checked throughout the property, including the roof space, and no issues were noted other than in the ground floor dining and kitchen area where a limited inspection of the sub floor area beneath the dining room showed an outbreak of dry rot (serpula lacrymans).

Discussion Damp: The two areas discussed, i.e. the living room and the dining room, share a common problem and the living room also has one unique to itself. Common to both rooms is condensation caused by a combination of infrequent heating and lack of ventilation.

This property has very efficient sealed unit double-glazing utilising PVCu frames. Both the living room and the dining room have gas fires inserted into the flue openings. This very common type of modernisation restricts the airflow through what were once prime sources of ventilation, i.e., leaky sash windows and the large opening of the original fireplace.

The gas fires contribute to the problem because they are used intermittently and do not provide the overall level of warmth which is available with central heating. They tend to be used ‘as needed’ but this strategy does not raise the temperature of the external walls sufficiently above dew point*, especially in colder periods. Consequently warm, moist air strikes the cold external walls and this, coupled with the lack of ventilation, allows condensation to occur. I believe that condensation will have been taking place intermittently, but to a significant degree, since the windows and gas fires were installed.

*Dew Point is the temperature at which condensation will occur. It varies according to the relative humidity in the room.

In the living room there is a further problem, which is attributable to the small flowerbed in the front garden. This flowerbed abuts the wall and its contact area corresponds exactly with the high moisture meter readings obtained internally. I believe this flowerbed is the cause of penetrating dampness into this area.

(As mentioned earlier, a wallpaper sample taken from this area and tested for salt contamination proved positive for chlorides and nitrates. This indicates the water bearing the salts has originated from the ground. Moisture that has not originated in the ground, e.g. condensation, will test negative for these salts. In addition, these salts are hygroscopic, i.e., they will absorb moisture from the atmosphere, and this will also contribute to the high moisture meter readings obtained)

In the dining room, the high moisture meter readings are almost certainly the result of ongoing condensation.

Timber: There were no issues other than that of the dry rot beneath the dining room floor. I cannot comment further on this until I have conducted a further examination. This is scheduled for Tuesday October

Conclusions Often, condensation is the result of ‘lifestyle’ with normal day-to-day activities such as cooking and washing releasing significant amounts of moisture into a building. In most cases people are unaware of the problem and, as its ramifications are not immediately apparent, do little to prevent it. However, there are things that you can do which will help considerably.

For instance, it may be that you are considering the installation of central heating and if so this should help to alleviate the problem. In the meantime it would be advisable to ensure that the ventilation in the two rooms in question is maximised by opening windows whenever possible. Also, when cooking and washing is in progress it will help considerably to keep the connecting doors between the kitchen and dining room closed. This will reduce the relative humidity in the adjacent rooms.

I would recommend the small flowerbed is either removed or at the very least isolated from the front wall and thus remove the cause of the penetrating dampness.

It may also be that there is a modicum of rising damp in both of the walls in question but I believe this is a minor issue and, given that the other problems are the main cause of the high moisture meter readings, I do not believe the expense or disturbance of inserting a damp proof course can be justified.

Other than the removal/isolation of the flowerbed and ongoing efforts to control the condensation, no further work is necessary with regards to damp problems.

Of course the discovery of dry rot is a major issue and no doubt you will wish to be satisfied that this problem has been cured prior to committing yourself to the purchase.

Surveyor Patrick F Doyle CSRT M. Inst. R.T.S.

Qualifications Certificated Surveyor in Remedial Treatments
(issued by B.W.P.D.A.)

Date of Report    October 2004

Signed Surveyor

Addendum: The timbers containing the dry rot were replaced with pre-treated ones. The moisture source that caused the dry rot was found to be the incoming water main, which, after it had entered the building, changed from Alkathene to copper, which was then routed via notches cut in the joists, to the kitchen taps etc. In order to insulate this pipe the owners had wrapped cotton sheeting around it but, because the pipe was invariably at a temperature that was at, or near, dew point, condensation occurred on it quite regularly. The cotton ‘insulation’ absorbed the moisture and consequently become very wet. As it was in contact with the timber this was enough to eventually trigger the dry rot. The pipe was re-routed and the problem is now solved.