To set the scene, the graph above relates to case of suspected rising damp. The property in which the samples were taken is a period age, solid wall construction building. One particular wall, in the lounge of the building had been affected by what was thought to be rising damp. The wall suffered from decorative spoiling in such that the paint kept flaking and bubbling after numerous re-decoration attempts. After a while, especially after periods of heavy rain, the dampness appeared to get worse. The concerned building owner, rather than asking a local builder as some seem to do, made contact to a national damp & timber company. Over the moon with the prospect of a free quote, a survey date was arranged.
Upon the inspection, the surveyor conducted a survey & after a short while diagnosed rising damp due to failed slate DPC. The building owner described how diagnosis was met on the basis of high protimeter readings at skirting level. The owner was subsequently given a quote to rectify the rising damp, including chemical injection DPC & re-plastering work. Works would total £4,300.00.VAT. The owner was prepared to pay for the works but decided on a second opinion.
I visited the property on a Saturday morning in early May. The weather was continuous with rain & quite chilly for the time of year. Upon inspection of the area affected, my initial thoughts were that the image in front of me was indicative of rising damp. There you go, it looks like rising damp, therefore anyone who recognises this & owns a damp meter could place diagnosis on rising damp.
As always, a holistic approach was adopted & all possible elements needed to be inspected. Adjacent to the dampness, on the outside wall situated a rainwater downpipe. Immediately this caused concern in a ‘bingo’ like moment. Rainwater downpipes, in periods of heavy rain can take massive volume of water. It is normal for a single down pipe to serve a whole elevation of a roof. Upon closer inspection, it was clear that the gully was blocked and backing up with rainwater. The ground surrounding it was also saturated & a split on the back of the downpipe caused saturation to the brickwork.
I proceeded to commence with moisture profiling inside, with the use of my protimeter. The base of the wall proved to be very damp in respect to damp meter readings. Subsequent to this, I decided to drill samples from the wall in a profile, starting at the very base of the wall, all the way up to the ceiling. This was undertaken as 1. The base of the wall was very wet and surface spoil was indicative of rising damp and 2. The downpipe adjacent showed to be saturating the brick face as well as the surrounding ground. Here we had 2 possible diagnosis’, rising damp or damp causing by a defective rainwater pipe. Of course, a repair to the downpipe & gully could have been recommended however to rule out any other source, gravimetric analysis was needed.
The graph included above may not mean a lot to some however what it shows us is that the base of the wall was very wet. 20% total moisture content was proved through the samples. To others testing with instruments such as a speedy meter, this may indicate certain rising damp however the sampling enabled us to distinguish between actual water and hygroscopic moisture within the total moisture content. The samples revealed next to no presence of hygroscopic moisture. In cases of rising damp, hygroscopic % levels are usually very high with the case normally being the inclusion of ground water salts such as chlorides and nitrates. What this told us is that the water saturating the base of the wall is free moisture. This indicated to us the source of the dampness was infact a defective rainwater downpipe & not true rising damp! Yes, the moisture is traveling upwards through masonry however it was as a direct result of a defective rainwater pipe.
Injection of a DPC was unnecessary & the original DPC is very unlikely to have failed as suggested. Our client was more than happy to see our results aside a schedule of recommendations which included a further inspection of drainage, a repair to the downpipe, some minor lime plastering & some skirting work internally. We estimated immediate repairs to be in the region of £2-300, quite a contrast to previous quotes of £4000+. This example highlights the importance of an accurate diagnosis & how it could save thousands of pounds.
Client care is paramount to us & we followed up our inspection up with a visit in August which proved our diagnosis was true. After suggested repairs, the wall within the Hampshire home showed no sign of dampness or decorative spoiling. A protimeter reading was taken for good measure which did not even register. One dry wall, one happy customer.
OC – Harewood Surveyors