Waterproof additive for rendering

Discussion in 'Builders' Talk' started by ayjvee, Nov 27, 2006.

  1. ayjvee

    ayjvee New Member

    Hi, I wonder if anyone can help?
    A single skin garage wall is wet internally (1.5m high wet/damp across wall)due to someone laying a patio behind it well above the dampcourse. This guy can't get his neighbour to sort the problem, so has decided to have the wall rendered. Please can anyone recommend a reliable/working waterproofing additive for rendering and who stocks it? Many thanks.
  2. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Hi, I wonder if anyone can help?
    A single skin garage wall is wet internally (1.5m
    high wet/damp across wall)due to someone laying a
    patio behind it well above the dampcourse. This guy
    can't get his neighbour to sort the problem, so has
    decided to have the wall rendered. Please can anyone
    recommend a reliable/working waterproofing additive
    for rendering and who stocks it? Many thanks.



    No. But I can imagine a problem if you are going that way.

    If the patio is above the dpc and causing problems, it must be close to, or touching the wall.

    You would need to render right down to the dpc.

    How you gonna do that ? Rendering down to the patio level is just going to make the problem worse.


    What you really need to do, is get down between the wall and the patio with tanking/bitumen, right up to and 6" above the patio level. Then, if you wish, render down to the bitumen level(although rendering would not be necessary after your initial treatment).



    Mr. HandyAndy - really
  3. ayjvee

    ayjvee New Member

    Hi Mr Handy Andy,
    Thanks for that, the patio is firmly cemented against the back of the garage wall, it's also probably sloping into it. I suspect this because the guy who 'built' it (It stands quite substantially above ground level) finished it at an angle against the wall and between 150mm and 250mm short! Instead of using materials that would drain the water quickly, he simply bodged a few cut pieces of slab where it didn't fit. I'd say he's at least 3 bricks higher than the dpc. Your suggestion is correct, but access to that side of the garage is firmly denied by the bloke who 'built' the patio, so any work has to be carried out on the inside wall off the garage.
    I was merely wondering if anyone could recommend the best waterproofer they knew of? Many thanks.
  4. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I was reluctant to ask the question, "I hope you don't mean, render the inside of the wall" because I didn't want you to sound foolish.

    Rendering the inside is not an answer. It will fail miserably.

    If it is your wall, you can force your neighbour to either rectify his cock-up, or allow you to rectify it.

    This sort of thing is written in the regs somewhere.


    Mr. HandyAndy - really
  5. jamison

    jamison New Member

    One word...


    Vandex.

    Go forth and vandex....
  6. jamison

    jamison New Member

    Seriously though, vandex is your answer here.

    It can hold back a river.

    You basically render a layer, score - then wait to dry.

    Then apply vandex with a brush.

    Splatter coat that.

    Wait.

    Then apply a top render layer.

    I'd advise adding the flexible additive to the vandex since if it ever cracks then water will p1ss through the smallest pinhole.

    You'd be amazed at how much damage a pinhole leak can cause.
  7. ayjvee

    ayjvee New Member

    Hi Mr HandyAndy,
    I fully realise that treating the inside of the wall isn't the complete answer, so I'm not feeling foolish. If I could gain access to his neighbour's garden I'd happily treat/fix it from there for him. With regard to your comment about legal access to his neighbour's garden, I've spoken to my local 'Building Control' and there is absolutely nothing written to stop this guy laying a patio against the back of the garage wall, either above, or below, damp, OR allowing anyone into his garden. I was told it was a 'civil' matter and a case for solicitors; I've now passed their comments on to the owner of the garage. I too, at the outset, assured the garage owner about access and repair on his neighbour's side, but it would appear I/we are wrong! So, the only way forward with his nasty neighbour is to try and shore up the inside for him.
  8. ayjvee

    ayjvee New Member

    Hi Jameson, I'll look into 'Vandex' later tonight. Cheers.
  9. dougalhouse

    dougalhouse New Member

    Hi,

    SIKA 1 is another additive. Available at Travis Perkins. We did a couple of basement conversions once (which believe it or not is below dpc and ground level) and used this in the rendermix then skimmed on top.

    If I remember rightly - apply a scud coat 1:1, allow to cure, apply a scratch coat (gently scratch enough for a key but not too deep) leave to cure then float as normal. All the coats contain the sika1 additive but check the tub for ratios.

    The only problem I can see is that we did all 4 walls with rounded corners to give a continuous 'seal' all round, whereas if you just do the offending wall the water will just go to the extremities and come where the render stops.
  10. dougalhouse

    dougalhouse New Member

  11. dougalhouse

    dougalhouse New Member

    So all 4 walls and the floor have to be done.

    But remember the water will still have to go somewhere!!
  12. jamisonc

    jamisonc New Member

    With reference to the water going somewhere - it should just soak away elsewhere, the fact that the OP's area below ground is tanked by vandex means it is protected - whoever else is next door or next in line will cop it instead... :)
  13. flyons

    flyons New Member

    If you are worried about the water "going somewhere else" you could inject a vertical DPC at the edge of the Vandex treatment.
  14. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Have the water pumped up and outfill onto next doors patio.

    Good for the goose, etc


    Look. Go out and collect a load of water damaged goods for nothing(say worth a couple of grand if it were new). Lay them up against your wall inside.

    Claim it on your insurance, and let the insurance company recover the cost from the pratt next door.

    Use the winnings to get a jolly good job done, and paint smilies on the outside.




    Mr. HandyAndy - really
  15. ayjvee

    ayjvee New Member

    Hi,
    Thank you all very much for the advice, which I'm now in the process of putting to the garage owner. He'll decide which way he wants to go with it. I'll also mention the insurance angle, but that's up to him too! :)
    Thanks again for your help.
  16. slapiton

    slapiton New Member

    there are proper tanking systems for below dpc that come with guarantees but are very expensive. where does the water go? you would need to lift the screeded floor and place a pump in the middle.then apply a membrane on the floor running up the wall at least a metre.the water goes behind the membrane and away through the pump to the nearest drain. all four walls are renderd normally and the floor screeded. fix the membrane with large plastic washers and plugs covered in silicone. use sika in the mix as an extra barrier. it works, we cured a soaking wet basement .
  17. Captain Chaos

    Captain Chaos Member

    My experience with sika 1 isn't good. According to the instructions it has to mixed in a special machine which looks like a vertically inverted cement mixer. I used it in a mix in a normal cement mixer and I have small patches of damp at the mortar joints through a cavity wall using 7n blocks.
  18. slapiton

    slapiton New Member

    you could ask the neighbour to lift the row of slabs nearest to the wall and lay a row of "aqua channell"drainage. the fall in the patio probably runs to your wall.

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