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Where is the damp coming from?!

Hi all, as in the title, I'm looking for some advice regarding our 'damp' issue please? Sorry in advance for this being quite long, please bear with me!

Most of our ground floor walls are damp low down, some worse than others, the worst have various tide lines on up to about a foot high, (that we can now see having removed walllpaper). This affects more external walls than internal, and large patches of the concrete floor, although it doesn't all look damp to the eye. We and our insurer initially thought that there was a leak in our CH pipes under the concrete floor somewhere. (Feasible as we had another leak like this last year).

After two visits from an SOS leak detection team and a plumber power flushing our central heating system (on leak detection's recommendation), no leak has been found.

The leak detection team have done two chemical tests on the wet plaster and they were both inconclusive, (apparently presence of nitrates indicates rain water but as I said the results haven't been conclusive).

We were told on the first visit that this inconclusive chemical test meant the leak was definitely from a 'clean' water supply, I.e. Mains water from cold water pipes, hot water pipes, CH pipes or mains supply outside our property.

On their second visit we've now been told that this is not the case and as they cannot find a leaking pipe anywhere, so the issues are down to rain water ingress, regardless of the inconclusive chemical test.

Their main evidence for this was by way of pumping some tracer gas in the ground outside our house, next to the brickwork below our damp proof course (1970s build so you can see the DPC), and detecting said gas inside the house, near to the site where it was pumped in outside.

Please can anyone tell me if this is standard practise and reliable for indicating failure in DPC, bridging through cavity wall insulation etc.? I've tried researching online but can only find information on tracer gas being used in pipes, not just into ground near brickwork?

The SOS leak detection team have now recommended that a structural engineer visits and assesses the cause of this rain water ingress, so we are waiting on that, if our insurer decides that our policy covers it which I'm not sure it will to be honest!

Any advice would be really gratefully received! Thank you!

Comments

  • phill99
    phill99 Posts: 9,094
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    If you have tide lines on external walls, I would be 99% sure it is rising damp caused by DPC failure or DPC being bridged. You seem to be going to a lot of effort to confirm something that most surveyors or decent builders would determine relatively easily.
    Eat vegetables and fear no creditors, rather than eat duck and hide.
  • Doozergirl
    Doozergirl Posts: 33,775
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    DPCs don't usually fail but every external wall?

    Maybe it wasn't fit for purpose?
    Everything that is supposed to be in heaven is already here on earth.
  • Mr.Generous
    Mr.Generous Posts: 3,333
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    How old is the property? I have seen things on older houses like plaster going down behind the concrete skirting and below the floor level. When chipped back the concrete floor must have been done after the plastering and it just draws moisture. Even when a dpc fails it wouldn't normally be every wall, but then again a plumbing leak is also unlikely to affect every wall and not show some other way. You might have to investigate one patch by taking it back to brick.
  • MRSB
    MRSB Posts: 53 Forumite
    Hi, thanks for the replies. Our insurance company have contractors in doing this work so we aren't in charge of what works are carried out.

    It's a 1970s house, and the worst affected wall is internal, but meets an external wall by our front door. That area has tide lines, while others areas are painted plaster and the paint is either bubbling/peeling slightly where I presume the top of the tide line would be, about 30-45cm up. We also have a 5 x 5cm patch of efflorescence on a wall about 20cm up, that had been newly skimmed though so I wonder whether that is why we haven't seen efflorescence elsewhere.

    I think I might get a builder in this week to have a look and see what a second opinion reveals. No other houses in the street have this issue as far as I'm aware, and they're all built in the same style.

    We wouldn't have got our insurer involved if we had if known it probably wasn't a leak, but as I said the worst area of these tide lines was revealed after removing wallpaper when we had already engaged with them and that's when other damp areas became apparent on close inspection. The surveyor they sent and SOS leak team did think it was a leak as well until their last visit.

    We've been outside today and have looked at all the brickwork/pointing etc. There is no obvious damage or material higher than the DPC as far as we can see. Atleast two courses of bricks under the DPC are visible all the way around the house. The only issue we found was damp bricks outside, under the damp proof course directly behind our garage guttering down pipe. Our garage is attached to the house, but the guttering is on the wall farthest away from the house and the bricks above the damp proof course appeared to be dry.

    Thanks again, as you can tell I'm not very knowledgable at all about things like this and it's quite scary that the issue is so wide spread.
  • phill99
    phill99 Posts: 9,094
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    Doozergirl wrote: »
    DPCs don't usually fail but every external wall?

    Maybe it wasn't fit for purpose?

    But they do. The old bitumen DPCs eventually get squeezed out due to the weight of the house. Where engineering bricks are used as a DPC, its easy to get moisture penetrating through the mortar joints over time.


    OP Some pics would be useful.
    Eat vegetables and fear no creditors, rather than eat duck and hide.
  • Furts
    Furts Posts: 4,474 Forumite
    I will approach this from a building perspective. Nobody can give definite comments without seeing the house. 1970s houses can be jerry built so you could have problems such as defective cavities and all sorts. I have rectified a damp house built in the 1980s where I found the problem was the cavities were filled solid with mortar to around 1 metre above dpc.

    However you need professional advice on what is going on. To say you have no idea and are leaving everything to the insurance company is truly scary. The insurance company will be clueless and looking to spend as little money as possible. They will also employ dubious characters who work for peanuts. All round an ideal breeding ground for bodging work and peddling nonsense to claimants. You need to fight this. It is your home, and you have a duty of care to yourself to protect your interests.

    Reading about a surveyor, and SOS Leak Detection, and pumping gas into ground sounds to me like pure snake oil sales people. Even the concept of thinking "I have damp in my walls so it must be a leaking pipe" is not a logical approach.

    Step back and do some deep thinking over all my points! You may not like what I say but I do know about building and I do know about contractors working for insurance companies.
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