TREATED DAMP STILL THERE

Discussion in 'Building' started by wossie6, 26 Oct 2005.

  1. wossie6

    wossie6

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    Situation is ,wanted cavitiy wall insulation ,but still got damp 4 years after treated,(reason why i have always had condensation).Had damp treated ie hacked off ,injected ?, tanked and replastered but damp is still there,i presume that dpc had been injected and that the damp is now seeping into concrete floor and carpets as it cant rise. I have a insurance backed guarantee and have contacted the company who did the work originally.But so far 2 appointments made yesterday and today have been cancelled.I had it looked at in the summer by same firm but i cant remember if he said the wall was damp,but he did offer me a lend of a dehumidfyer but i got one already, i had a rad fitted on to the damp wall as i started getting mold on the wall,the copper pipe has turned green.
    What i want to know is why is there still damp, how is there still damp and why they did not find and fix the problem,and not just patch it up,i am annoyed that i feel fobbed off and as i redecorated bedrooms and with the condensation i have the new wallpaper has turned black.

    What questions can i ask ,i dont know much about damp but i want it sorted for good.
     
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  3. Softus

    Softus

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    The causes of damp are many and varied, but it does not rise through brickwork, so injecting is utterly pointless (although many damp-proofing companies will tell you otherwise).

    Your damp could be falling, for example from a leaking gutter, or by leaking onto the top of the inner skin and running down the outside of that skin.

    Or it could be rising, which would mean that it's travelling, by capillary action, between the brickwork and the plaster (internally) or between the brickwork and render (externally).

    If the damp is rising inside then you may have a faulty DPC - a functioning DPC will cover the entire floor and also be continuous with the DPC within the wall.

    Or, the damp could be hitting the wall sideways - this occurs either by driving rain, or by bouncing off hard ground that is too high next to the wall.

    Or, it's condensation. This will tend to form near the top of a wall where the air is most moisture-laden, so if your plaster is getting damp at the bottom of the wall then it's unlikely that condensation is the cause.

    Does this help?
     
  4. wossie6

    wossie6

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    Ta for reply,

    plasterwork does not feel damp although ill have to wait tommorrow when damp surveyer comes round ,if he keeps it,,its the brickwork that i can feel behind,(there is about a 3 inch gap )from floor to where plaster starts.I was on the understanding that damp does travel up brickwork,house was built early 1900 and does not have a physical dpc.If damp does not travel up brickwork,how does rising damp occur in the first place.And why are the bricks damp and why is the carpet wet,where it touches the brickwork.
     
  5. Softus

    Softus

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    What can I say? It just doesn't.

    See my post above - it rises by capillary action, between the brickwork and anything that lies very close to it. This will make the bricks wet, not vice versa.

    The point of the physical DPC in the wall is to connect to the DPC in the floor and prevent water rising between the floor and the brickwork. If the water table has risen under your house and you don't have a DPC in the floor, then you have a problem.

    I had exactly the same problem as you in my downstairs bathroom when I bought my house (it's about 80 years old). The damp was so bad that the tiles were falling off the TOP of the walls. Water was running into cracks in the render on the outside, and was rising directly through the earth under the concrete floor, through cracks in the incompetently laid screed, and in the hairline gap between the floor and the walls. It was almost a swimming pool.

    I dug out the floor to about 18", laid a slab, painted the walls below and up to the DPC with Aquaseal bitumen, laid a DPC in the floor, screeded on top, and hacked off the faulty render outside and haven't even put it back yet. Hey presto the room is as dry as a bone, and has been for 5 years.

    There is no such thing as damp that rises through brickwork. If you can find proof then I will eat those bricks.
     
  6. Nige F

    Nige F

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    So all bricks are totally imporous, and the damp goes round the mortar :rolleyes: Where did you do your bricklaying apprenticeship
     
  7. Softus

    Softus

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    No - you're wrong. Most bricks are porous.

    Are you suggesting that a wall with cracked morter will draw up water? If so then why not just say so?

    BTW, if the morter is cracked then injecting a DPC will achieve nothing.

    What are you talking about? I haven't served a bricklaying apprenticeship, or at least not at a college. Are you implying that I'm not entitled to have an opinion about rising damp?

    On the whole you're way to oblique for me Nige - I doubt that your irony will help wossie6 either.
     
  8. JayS

    JayS

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    Which means there will be capillary forces working within them... I fact the smaller the pores are the higher the water will rise. That would imply that water would rise higher within a brick then within mortar...

    Here it is all explained...

    [​IMG]
    "Capillary forces can be illustrated by a group of small capillary tubes with different diameters (see Figure 5). If the capillary tubes are placed with one end in a pan of water, the water would rise into each tube. The height of the water in each tube would depend on the diameter of the tube. The smaller the tube, the higher the rise. The surface tension of the water itself and the diameter of the tube cause the water to rise. The water must be under negative pressure to rise. Because this capillary phenomenon can operate in any direction, it is the key to water retention in soil pores. The pore geometry is much more complex than the simple capillary tubes, but the water is under negative pressure due to the capillary forces."

    I'm not saying a chemical damp proofing is the correct way to go. Personally I think if it's an external wall where you got access to all of it I think a substantially better way is to remove the mortar between two brick layers a fit a proper plastic (or similar) DPM. This is a tedious and expensive process but it's unlikely to ever fail again...

    Chemical damp proofing might be the only option in some cases. Properly diagnosed and used I don't think there's anything wrong with it as such...

    From what wossie6 is saying (we could do with some more info here!) I get the impression it's not damp down at floor lever with salt residue on the wall, which would be the case if it was a broken DPM causeing capillary (rising) damp.

    The problem sounds more like condensation to me...which is caused by poor ventilation...
     
  9. wossie6

    wossie6

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    ok result,but think agai8n ive been fobbed off,tested and his meter went red in places and green in others,butall he suggested that the render should be knocked off the external wall (party wall)and that it would take a few months to dry out,hmm so how can a damp external wall make an internal wall damp,(cavity full of crap)?although he did not try to sell me anything and that he reckons that my insurance backed guarantee is void due to the render,if this is the case why was i not informed by damp company4 years ago.Istill feel fobbed off,but he did suggest that he would have a word with the cavity wall insulators.

    yes i do have condesation but that is upstairs,this is at the bottom of the stairs,there is no runs on the wallpaper,can see the damp on the concrete floor ,green copper rad pipe,will post pics at the weekend cant get pics yet as light is not good before or after i finnish work.
     
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  11. Softus

    Softus

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    No it doesn't. Whilst there's nothing wrong with your 'O' level fluid mechanics lesson JayS, we're talking about what happens in practice. Where did you find the evidence that the pores in a brick all meet up in a handy way like a tube that connects the underside of the brick to the topside?

    Here's an offer - if you can build a brick wall three courses high, and get water to rise from the bottom one to the top one merely by the "force" of capillary action through the bricks, then I'll deliver you a free keg of your favourite ale.

    No, no, no, no, no. No. Chemical damp proofing isn't "the only option" - it isn't an option at all because it doesn't achieve anything with undamaged bricks.

    FYI, salt residues are common where damp has previously risen behind the plaster and soaked it. The plaster has to be replaced, and it's standard practise to hack it all off from the ground to three feet up, and let the wall dry out before re-plastering.

    Why would there be condensation at the bottom of the wall?
     
  12. Softus

    Softus

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    Yes - you have I'm afraid.

    Maybe I don't understand what a party wall is, but isn't it a shared wall, and therefore doesn't have an external surface, therefore won't be rendered?

    Does this mean that the wall was rendered after the dp company did its work?

    Because you were robbed.

    On the face of it your man-with-the-meter sounds as though he knows his stuff. I suggest you stick with him until the problem is properly diagnosed.
     
  13. wossie6

    wossie6

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    mmm nice reading,

    dont want to be flippant but the wall im talking about has been rendered,it was rendered for years even before i moved in

    guarantee cant be void as it was issued with the rendered wall.

    man with meter might know his stuff but he was quick to say his insurance backed guarantee that his company supplied was invalid even after asking ,how long the render had been there.i would of thought a selling point on his behalf and claiming on the guarantee.
     
  14. Nige F

    Nige F

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  15. JayS

    JayS

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    Ehh, I'm not arguing with anything you're saying Softus...I will now though...this is pretty basic physics...

    Bricks are made of a porous material so you will get a capillary action in in them. A brick is pretty much the same as a sponge (except harder). Leave a brick in a bucket of water for a few weeks, knock it in half and it'll be thoroughly soaked.

    Let me give you an example from personal experiance. I was doing some electrical work in a house recently, the house was built with breeze blocks like many modern walls are (and cladded with bricks on the outside). Breeze blocks are made of a very porous material so they soak up water nicely... Anyway to cut it short. The plaster looked fine on the top, but when I started drilling holes into the breeze block it was very moist! Further investigations showed the breeze blocks were sucking up water from a connecting wall, alas bridging!


    Yes you should replace the plaster, not disagreeing. But it want sort the damp problem will it? It will only 'hide' the damp. You'll have to fit a DPM, preferably a nice think plastic sheet! :)

    Sounds nice! Might take you up on that. :) Only problem is, it's a very slow process so I'll let you know in a few years... :rolleyes:
     
  16. Softus

    Softus

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    What? I take it that you don't have any sensible technical answer?
     
  17. Softus

    Softus

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    Yes it is, but you have to take reality into account.

    Bricks are bricks, not sponges. Your dumbing-down of the explanation has merely distorted it beyond credibility, not acted to make it correct.

    That's all very nice, but any assertion that the damp was rising through different courses of blockwork is conspicuous by its absence.

    You must NOT replaster until the damp problem has been remedied AND the wall has dried out, or the new plaster will become wet.

    The problem with wet plaster (once cured of course) is that it loses its essential properties, one of which is be able to stick to the wall.

    Please do. I mean it. In the meantime, have you experienced any real-life examples of rising damp caused ONLY by a failed DPC in the wall? In fact, I'm motivated to start a new topic...
     
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