Hi all,
Forgive me in advance as this is long...
We have an ongoing damp issue in our kitchen on an internal wall. This is an original wall (1850s construction) and the kitchen is an extension built in 2005. We moved in last year and I've been trying to figure out this issue since.
Initially had some damp patches on the highest portion of the 'pillar' - our usual builder believed this to be gaps in upstairs' bedroom window sill where they hadn't removed the old timber frame when replacing the windows. This was sealed, he took the wall back to brick, let it dry out for 3 weeks. It was seemingly dry so he proceeded to apply two coats of tanking slurry (yes, I know. I know now this shouldn't have happened. Please go easy on me!!). He wanted to put a vapour board (?) on there but I said no as by that point, I had started to read up more on this and was panicking.
He put plasterboard and then skimmed it, presumably with gypsum. Left this to dry for 3 weeks and then these weird damp patches started to appear. They have gotten bigger over time, and sometimes shrink, sometimes expand. The holes there are where another builder chased.
We had a leak detection survey which showed the moisture was just concentrated around the damp patches but there were no active leaks in the kitchen. He tested the salts and found high levels of nitrates (liquid turned red) plus chlorine, so suggested we get a CCTV drain survey to check if there was a leaking waste pipe underneath us that had a crack and was drawing up the moisture from the ground... He said high levels of nitrates like that indicate waste water.
This CCTV survey showed that the pipes running underneath the problem area were fine, there were some minor cracks near the downpipe drain (other side of our small kitchen but not particularly near the problem area). I've filled these in now as well as some minor cracks between the bottom brick and concrete floor outside (below the DPC).
There were cracks in the soil pipe line that serves our bathroom plus two of our neighbouring upstairs flats - will get this fixed, but this is again not near the problem area and is on the other side of the flat. Not had any damp issues there.
The flat roof has been checked and flashing is fine, no water ingress around there and leaks had been ruled out using a thermo imaging camera.
The CCTV guys were suggesting it might be time to dig up around the wall and assess where the moisture is coming using dyes. This is obviously a distressing suggestion as it's going to cost enormous amounts of money we don't have to carry out and then make good. We are also expecting our first child in 6 months and I'm desperate to get this resolved before then.
I asked a few people knowledgeable about maintenance of old properties and they said it's likely excess moisture from the lack of cooker fan. We have a recirculating fan (probably barely working by now and they said this, coupled by the use of modern materials on an old original wall, is preventing the wall from breathing.
We do dry clothes in this room also, but dehumidifier is practically always running.
I would really appreciate any advice you folks can give.
Thank you.