‘That’s not rising damp – it's condensation’
A housing association was told that this property needed a complete new damp proof course and associated re-plastering. My investigation revealed the problem to be condensation – not rising damp.
Instructions: Inspect ground floor walls for possible rising damp.
This property is owned by a housing association that uses me to inspect ‘problem’ properties. The property is a detached two bedroom, two reception room residence constructed of solid 9” brickwork. The tenants had complained of damp problems and the housing association had instructed a damp treatment company to inspect the property in February. The treatment company reported that the whole property needed a new damp proof course and replastering. This would necessitate the tenants moving out for 10 -12 weeks whilst the work was undertaken and reinstatement work completed.
Upon arrival at the property the tenants showed me their main areas of concern which were a rear right corner of the right side reception room and beneath the work top in the rear right corner in the kitchen (Fig: 1 & 2).
In the reception room a settee was present in the rear right corner which was pulled forward revealing mould growth on the wall surface and wall paper which had lost adhesion. Beneath the kitchen work top a similar situation was present. I used on the wall surfaces a resistance moisture meter and a moisture meter in radio frequency mode (this mode ignores surface moisture and detects moisture beneath the surface). I was not able to detect any increased moisture presence at all. I checked all other accessible walls throughout the ground floor and with one very small exception I found no significant active damp problems. Externally I noted that the property had already received two previously injected chemical damp proof courses.
Based upon my inspection, visual evidence and information provided by the tenants I concluded that the problem in the property was condensation which will become apparent again during the cooler winter months unless the tenants change their style of occupation. The tenants openly admitted that they dried all of their clothes in the right reception room and they told me in winter they see water actually running down the walls. Even at the time of my inspection internal clothes drying was taking place despite the fact that it was a bright sunny day. I also noted no windows were open.
I sensed a humid atmosphere in the property and unusually for the summer months I carried out a condensation check and as expected no surface condensation was occurring. However at the time of my inspection the outside air temperature was 19.3ºC and the relative humidity was 61.6% which equates to a vapour pressure of 1.37kPa (Kilopascal). Inside the air temperature was 22.9ºC and relative humidity was 62% which equates to a vapour pressure of 1.72kPa. The vapour pressure inside the property was greater than the vapour pressure outside the property which is normal in most residential properties in the UK for 90%+ of the year. The vapour pressure differential between inside and outside at the time of my inspection was 0.35kPa which BS5250 categorises as ‘moist occupancy’ and goes on to state this is ‘Where ventilation does not quite balance moisture production/large water production’.
The tenants were very relieved that the property did not have a rising damp problem and that they would not have to move out of their home to have work undertaken. They were grateful for advice on how to reduce the problem of condensation during the cooler winter months and wanted to upgrade the loft insulation as part of this.
This was one of a batch of three properties I looked at for the housing association.
1. This property required no work other than educating the tenants to understand the causes of condensation. A damp treatment company wanted to treat all walls and had not mentioned condensation despite undertaking their inspection in February 2010 when it was very cold and almost certainly condensation would have been in evidence.
2. The second property required damp treatment of the front elevation only despite the fact that a damp treatment company said all walls throughout the ground floor needed a new damp proof course – I actually located a new physical DPC which had been cut into many of the external walls of this property.
3. The third property was vacant and my findings were similar to those of the treatment contractor’s.
The housing association were very relieved that no extensive damp remedial works were necessary in two of the three properties. This would save them the considerable expense of having to temporarily decant two sets of tenants, the cost of DPC works, re-plastering, redecoration, removal and re-fitting of radiators, sink units, electrical attendance etc. They estimated that this would save them in the region of £5000. The housing association were going to take issue with the damp treatment company who appeared to be specifying unnecessary work.
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