This Victorian house has been badly treated, the owner bought last year knowing that there were problems with it.
The property has twice had chemical damp proofing treatment, the suspended timber floor was replaced with a solid floor. The skirting board had Dry rot. The damp looked like a leak, being spread out, with a central point under a radiator. Damp proofing treatment mask the dampness in walls, but did not stop it. There are suspected hygroscopic salts from the chimney breast.
- This was a complex survey. I said with some certainty that I though the root cause was a leaking central heating system, at this a heating engineer should pressure test and disconnect a pipe to check for a leak.
- Dampness is walls is being hidden by past damp proofing treatment and impermeable slurry, this makes it:
- harder to find the centre and therefore track down the leak,
- explain to clients why one wall is apparently damp, and another not,
- There was no mainwater leak, but the client told me that they have had to top up the centraal heating system twice over the winter.
- Unless we can see a leak, determining that a leak is the most likely root cause is as a far as we can go with leaks. Other companies specialise using tracer gas etc, such as LeakBusters.net (this is not an endorsement).
Leak from the central heating system, almost certainly within the wall connecting the kitchen to rear reception.
There have been at least two attempts at damp-proofing the house.
Trying to work out the effects of mis-diagnosed and mis-treated damp is complex.
Opening windows for an hour a day is hard to prove. It infers that condensation is an issue.
There is Dry rot in the skirting board, although this looks old, it would be odd if it was not picked up by contractors during their quotes. Dry rot is needs water to grow. I don’t believe rising damp or hygroscopic salts cause Dry rot. For this reason I believe there has been a leak. I tested and did not find a mains leak suggesting that the leak it’s from heating.
The suspended timber floor has been replaced with a solid floor, suggesting that Dry rot has been a problem for a while, see later in this report.
The dampness here is centred around the radiator.
The dampness in this area does not look like hygroscopic salt damp.
The radiator valve has a dribble mark below it. I understand the heating system has needed to be topped up. It is possible that at high temperature and pressure the heating system is leaking. This should be checked with a plumber.
Rainwater flowing down a rendered wall can enter through any gap and track back inside.
Calcium sulphate is a key ingredient in cement and other building materials. If diluted in water salts tend to move to the surface. These can be removed with sandpaper and painted. Plaster appears to be touching the solid kitchen floor, this will exacerbate any problems. Consider cutting the plaster back by 1cm from the floor, under the skirting board.
When radiators are not used they are cold, increasing the risk of condensation.
I tested the surface on the inside at the base of all external walls every metre, chimney breasts and a sample of internal walls with a Protimeter damp meter in conductance mode. These meters measure electrical conductance of salts in water, a proxy for damp. Readings below 20WME are considered dry. The range is 8 to 99WME. See surveyor.tips/dampmeter.
The potential causes, are: 1) the radiator fixings penetrating the slurry resulting absorption imbalance, 2) condensation from a cold radiator, 3) a leak running across the solid floor.
This would not be the case if that was rising damp unless of course the wall has different absorption rates, which in itself can cause localised dampness were one section of wall is absorbing moisture and the other section is not. The solution comes from improved ventilation and heat balance.
It’s difficult to be sure of the source of moisture here but given the other issues it is likely to be either condensation or a radiator pipe leak.
I also tested walls in radio frequency mode. Water reflects radio waves at a set frequency similar to mobile phone shields. Meters can’t differentiate moisture from other dense matter such as metal and concrete. They help trace damp in a normal, homogeneous wall.
Readings below 300 REL indicate that a wall is dry below the surface, 999 REL is the limit. These meters are for scanning, mapping and profiling, see surveyor.tips/profile.
Render cracks should be filled by Thermoflex and windows sealed with sealant like mastic.
The gulley was not blocked but it is possible that there is a crack underground. You should consider bypassing the gulley and drain, which is over 100 years old, and extending the downpipe to the road, as many houses do.
The dampness is causing mould to grow on the roofing timbers.
A damaged chimney pot and lack of cowling on any of the pots, including the neighbours, could account for the dampness in the loft. This is not a roofing survey and there was no resulting internal dampness.
Client sent images
Follow-up remote consultation
All the data and profile etc. points towards a leak and probably above ground, rather than underground. There was no movement on the dial of your mainswater meter when the water was off, but there was when water was flowing (you should double check this) – there could be a fault with the meter, but it seems unlikely.
- The leak could come from your neighbour and you should check that, but again this seems less likely that a heating system leak.
- Therefore the most likely source of the leak is your heating system, which has had to be topped up regularly.
- I can’t test pressure loss on the heating system, but I note your 2 smaller heating engineers said they could, but don’t have leak tracing capabilities.
- The walls have been damp proofed against rising damp which typically uses impermeable slurry up to about 1.3M. Slurry acts like a like dam or swimming pool wall. The water is probably being absorbed deep into the wall, finding its way out through imperfections or around the edges of the slurry.Water can easy traverse under or above the damp proof membrane in a solid floor. Dry rot spreads itself out through spores and strands.Water is the bi-product of respiration, so Dry rot starts in a gloss painted skirting board it can easy grow through it.
If I were a betting man, I would say the leak is most likely in the wall coming from one of these two radiator pipes.I understand that you will probably want to replace this radiator anyway at some stage. I’m not at your property and am not a plumber. However, if it were me, I would consider asking your plumber to:1) pressure test the heating system for a leak, these can be indicative not conclusive (you can get false positives and false negatives).2) consider disconnect these pipes from the kitchen side, probably reconnecting them to each other so that the central heating can flow.3) then carefully remove each pipe from the wall and inspect for a leak.
Leak detection is complex and outside my remit. Using slurry to hide dampness is very expensive and dangerous, as you can tell.By identifying the leak correctly, you will not only save yourself around £12K (from memory), but also ongoing risks of rot and “leaking slurry”.I am hesitant in what I say and write as I can’t be held responsible for any damage associated with these pipe or any other source of water. I can’t tell you exactly what to do as there are so many other potential sources of water, but if I were trying to save £12K, I would start by eliminating this the most likely leak.
There was damp around the cold-water stop cock, under the stairs. The most likely reasons are:1) it is close the suspected leak, and 2) cold water pipes reduce temperature to about 8°C in winter, slowing down the rate of evaporation and can cause condensation.