Rising damp?

I got a call from a friend of a friend who had been suffering from persistent rising damp. He has spent a fortune on various remedies but it still it came back. The flat was only twelve years old so it sounded to me as if the damp proof course had been breached in some way. The usual reason would be having a path or patio laid to close to the dpc height.
When I arrived at the flat I was somewhat surprised to find that it was on the third floor. I have seen a lot of cases of rising damp in my time but never has it risen above 1 metre. I was ready to rule it out but when I got into the flat I could see all the familiar signs of rising damp. Large patches of bubbling plaster up to a height of around 900mm. Some patches were on internal dividing walls and some patches were on the outside walls or party walls to neighbouring flats. None of the other flats in the block had shown any signs of rising damp.

The patches seemed to coincide with radiators and my immediate thought was that the central heating system was leaking. “I’ve had it checked” he said.
I subsequently found out that this problem had been going on for two years and a surveyor had originally diagnosed a central heating leak some time ago. The only problem with that diagnosis was that the system showed no pressure loss. This could of course have been because it was being slowly topped up by the filling loop so I disconnected the loop just to make sure and I told the householder to keep an eye on the pressure gauge. A week later there had been no sign of a pressure drop.
“I think we can rule out the heating” I said .
“Yes that it what the plumber told me” he replied.
The householder then told me that he had a damp specialist company in around a year ago who had re-plastered the walls with a waterproof render. This is treating the symptom not the cause and judging by the bubbles and flaking plaster it hadn’t even done that. All that work and disruption hadn’t made the slightest difference.

It occurred to me that if the pipes feeding the radiators started in the hall cupboard where the boiler was and spread out like tentacles through plastic duct work set in the floor screed it was just possible that the duct work was also shared by another pipe which was leaking into the duct. The obvious place to start was in the cupboard. Unfortunately there was no sign of any duct work in the airing cupboard but I found that the pipes went through the wall and down under the bath. The bath panel was tiled in with no visible means of removal and that could have been the reason why nobody had pursued this line of enquiry.

When I eventually managed to remove the panel I could see immediately that the flexible overflow pipe had fallen off at the top end and it was dangling in the plastic floor duct. This meant that a good percentage of the water from the bath or shower was leaking into the ducts on a daily basis and was then being channelled around the house by a system of what were effectively small canals. The canals came to an abrupt end at the walls which not surprisingly were very damp.

I put the hose back on the spigot and secured it there with a Jubilee clip. The total cost of the repair 26 pence.