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Cutting down through DPM for waste pipe

Discussion in 'Building' started by Steve Spits, 19 Sep 2017.

  1. Steve Spits

    Steve Spits

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    Hello

    I intend to fit a new ground floor toilet in my early 70's house which has a concrete slab as the ground floor base, which will involve inserting a new soil pipe connecting to the existing set up. I am assuming that in doing this I am obviously going to breach the DPM.

    So two questions:

    1. What is the best way to cut into the slab that will cause the least damage to the existing DPM i.e. to do it as neatly as possibly to make repairing as easy as it can be. Would using an angle grinder be the best bet or some sort of pneumatic hammer?

    2. When the job is complete and the new soil pipe is in, what is the best way to reinstate the new DPM, would I have to lap the new and old bits together?. If so how do you expose a sufficient amount from the old DPM in order to do this.

    Thanks in advance


    Steve
     
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  3. tomfe

    tomfe

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    Cut out your section with a saw then use a hammer, electric or manual, to break out the concrete.
    1970's should have a plastic DPM, you'll end up puncturing it no way around it, try and get an over lap around the edge onto the existing and gunk it up with silicon and place your new DPM on top make sure there is plenty of squeeze out. If you are still worried use a liquid DPM on the edges of the existing slab.
     
  4. Ian H

    Ian H

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    If you cut the concrete you will make a huge mess.

    Can't you send it out through the wall?
     
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  5. pilsbury

    pilsbury

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    Although not retro fitting, when I put my new DPM round the soil pipe coming up through the floor, I made sure it wrapped up around the soil pipe. For joins I use a double sided DPM tape - a bit like super tacky plasticine.
     
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  6. Steve Spits

    Steve Spits

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    Possibly could go out through a wall, it wouldn't look so neat but may be an option. Thanks for your replies
     
  7. Ian H

    Ian H

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    I took mine out through a hole I cut with a £70 Mexico core kit. Nice and neat.
     
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