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Rising damp does not exist

Discussion in 'Building' started by Softus, 28 Oct 2005.

  1. tawelfryn

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    I agree with everything you say Softus, there is dpm under concrete floors, 1800 gauge now, thicker than 10 years ago, was using 1200 or even 1000, I don't know what the gauge is only know its thicker! That is then overlapped on the internal leaf of the dwelling and dpc laid on top. The EXTERNAL leaf dcp is at the same course, only its origin is from a 450mm wide dpc which is fixed one course of blocks higher on the INTERNAL leaf, producing a damp tray, thus any moisture or water from cavity ties fall and is made to go outside via weepholes in the perps. Theoretically it is all damp proofed internally with an EXTRA dpc one course of blocks (225mm) on the internal leaf.
    When this is done properly, it is IMPOSSIBLE for moisture to rise on the internal leafs wall covering, like you say is the most common, and I also agree is. Damp trays are also put above all openings as we all know AND common practice is to "seal" each floor with a complete tray all around a dwelling (especially on these "hip city apartments" springing up everywhere) I've always known them as flats!
     
  2. Softus

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    Hurrah! Are you up for a T-shirt?
     
  3. ModernMaterials

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    At the risk of sounding rude.......

    Can anyone tell me what Conrad's remedy is for hygroscopic salt build-up?

    No offence Conrad but smart as you are, your English reads a bit like the handbook for my cheapest taiwanese camera...(need not the drive for fabulous plugplay pleasure etc...)
     
  4. jbonding

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    Unless you live in a sponge how can rising damp happen or exist, ive heard if its not this or that then it must be RD. ive learned how plastering works and rising damp was bandied about and i was taught how to remedy damp as in waterproofing. But was never taught about rising damp, has anyone been taught this or teaches this or is it something that is being mentioned in a sylabus because its BR. How can drilling holes and injecting fluid work, does this rise?
     
  5. splinter

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    If rising damp does not exsist which I don't exspect it does after reading this post,you all to admit it is one of the best ,greatest scams in the building industry in the last fifty years :eek:
     
  6. joe-90

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    Have any of you ever seen a damp course being pressure injected? As the fluid goes in it displaces the water in the brick and the brick 'sweats' until the water runs down the brick. The water that comes out is crystal clear. Can someone tell me where that water comes from on an internal wall?

    It can only come from the ground rising upwards.

    I've seen it. RD does exist.


    joe
     
  7. noseall

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    i bet , i could walk into any building (modern, old, damp, dry or otherwise) armed with a damp meter and a mouth full of spit (or a bladder full of p**s ;) ) and show that all the buildings have "rising damp". what a con.
     
  8. splinter

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    Idon't know why but I find this post interesting ,it might have something to do with the size of my anorak!
    Anyway Joe90 , just out off interest (and this is not a loaded question).What volume of water "Sweated" out of the bricks.Do bricks have any " naturual " water content,what was the highest point in the brick work above the DPC were water "sweating" out,are you a chatholic and seen the "stigmata".........
     
  9. ModernMaterials

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    As i understand it, the stuff being injected is a suspension of silica in liquid paraffin. The paraffin has 2 functions. It carries the very small solid particles and repels water from the pores of the brick, allowing said particles to remain in the pores. The guy doing the injecting waits for the paraffin to bleed through the brick for a while before turning the jet off.
    Initially, the paraffin drains down the brickwork before finally dissipating through evaporation.
    So, what you are seeing is mostly paraffin and this is yet another case of 'not proven m'lud'.
     
  10. Softus

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    Yes - plenty of us I suspect.

    I hope you don't me asking - how do you know that it is water?

    If it is water then it could easily have come from the lungs of the humans who live there, but how do you know that it is water?

    Does the ground contain more water than the ambient air then? If so, what are the relative quantities?

    I hope you don't me asking - where have you seen it, and how was it diagnosed?
     
  11. anobium

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    Can I just point out that silicone injection comes in two types.
    Type 1 lines the pores of the the brickwork/masonary, and type 2 blocks the pores, thereby preventing the capillary movement of moisture.

    Softus how can you say that on one hand you can accept moisture moving up the wall between the face of the brickwork and plaster, and yet on the other hand you say you cannot accept rising damp.?
     
  12. Softus

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    I've highlighted the bits that are particulary pertinent to your question anobium.

    Now then, I've only ever said that I can't accept it without an explanation of a real-life occurrence, so please tell me where I've said that I cannot accept rising damp.

    To answer your question directly, I can say that I "accept moisture moving up the wall between the face of the brickwork and plaster, and yet on the other hand cannot accept rising damp", like this:

    I can accept moisture moving up the wall between the face of the brickwork and plaster, because I have first hand experience of it and have a scientific understanding of how it can happen, but I don't accept rising damp through brickwork because I don't have either.

    Answer me this if you would: is it unreasonable of me to seek a clear explanation to a widely-accepted phenomenon, and to remain unconvinced of its existence until I can read such an explanation? After all, we're not talking belief in Christ here, but there are plenty of people who claim to have seen RD, and yet can't describe where it happened and can't explain how it happened. There are plenty of other people who have a scientific explanation but no real-life example.

    For something that you believe to be so straightforward and easy to find, why do YOU find it so hard to explain how it occurs?
     
  13. anobium

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    Softus ,I think we are all in danger of tying ourselves up in knots on this topic.
    Firstly has I know it rising damp is a natural phenomena caused by the upward movement of moisture through certain materials by capillary action. This is not just the opinion of the industry in this country but also the opinions of those in the USA and Australia plus also the companies who manufacture bricks.
    It is not as you said caused by the failure of a damp proof course.The dpc merely stops it rising above a given point.
    I personally have seen rising damp on bare brick internal dividing walls .
    How have I come to the conclusion that it was rising damp, by the following.
    Firstly I examined the walls in question for the presence of any water pipe that could be causing the problem.
    Normally one would check externally for possible defects, but as I said this was an internal wall so it was not necessary.
    I then took samples of the brickwork and mortar joints starting from the base of the wall and then at approx every 300 mm intervals approx two thirds into the wall upto a height of 1 metre These samples were then placed in airtight bags and then sent to a laboratory with a request for them to be analysed for the total moisture content and the free moisture content.
    The free moisture content is the total less the hygroscopic moisture content.
    In this case the results came back showing a free moisture content of 15% at the base of the wall reducing to approximately 7% 1 metre high.
    From these tests I concluded that the wall was suffering from rising damp and I recomended that a new dpc be installed.
    For the record the wall eventually dried out , but not immediately as it was 325 mm thick.
    I should point out that I have had cases were the hygroscopic moisture content is greater than free moisture content, and in these cases the cause of the dampness would be classed as being hygroscopic and would therefore not require a new damp proof course
    I would however agree with you and many other posts on this subject that rising damp is misdiagnosed in the majority of ocassions and damp courses are inserted unnecessarily.
    Hope that this goes some way to answer some of your misgivings on my previous posts
     
  14. jbonding

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    Is there such thing as descending damp? If there was would the symptoms be similar? Where does the condensation actually go, lets imagine it goes down the bricks, the symptoms would be the same? Is a damp course making things worse by not letting the descending damp leave?
     
  15. anobium

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    Yes there is descending damp, ie from defective gutters, slates, etc.
    However the profile of the dampness would be different. For example and I am generalizing but normally the moisture content would be greater at the point of ingress, ie higher up the wall, and reduce gradually lower down.
    Rising damp cannot go much higher than about 1.5 metres up and the dampness reduces as you go up the wall.
    There is also lateral moisture penetration , ie through defective pointing ,rendering, wall ties, etc,and each one will give a different profile in the dampness readings.
    The biggest problem is sometimes you can get falling/descending damp, penetrating damp, and condensation, all at the same time, particularly in a building that has been empty for some time,and in those cases you can only identify if rising damp is a factor when you have rectified the causes of these other problems.
    As it can take many months for a wall to dry out , in some cases more than a year, you can see why sometimes a damp proof course is installed
    without really knowing if it was necessary.
    A damp course cannot make a damp problem worse even if it is descending damp.
     

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