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Waterproofing a control flange after screed

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  1. #1
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    Default Waterproofing a control flange after screed

    Hi all!

    Im almost up to the waterproofing stage of the bathroom and laundry reno, and have a few questions.

    In the bathroom (1950's floating concrete slab), there is a concrete skirting around the edge, which made the installation of the pvc flashing virtually impossible to get flush with the floor. I managed to get it in there but there is a gap between it and the floor. The surface of the slab is also quite poor, with divots etc, so my plan was to screed the slab (and pack some concrete under the flashing in the gap), then waterproof afterwards.

    Questions:
    - The plumber has installed 2 control flanges on the floor for the 2 drains. What is the best way to screed around these without tipping concrete down the pipe and ending up with a nice finish?
    - A builder mate of mine said that since this house is a rental, he would recommend putting the waterproofing under the screed, this way if the tenants chip a tile etc, the waterproofing membrane remains in tact. I just cant see how this is physically possible given the condition of the slab. Thoughts?

    Cheers,
    Mrpotatohead

  2. #2
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    Quote Originally Posted by MrPotatohead View Post
    Hi all!

    Im almost up to the waterproofing stage of the bathroom and laundry reno, and have a few questions.

    In the bathroom (1950's floating concrete slab), there is a concrete skirting around the edge, which made the installation of the pvc flashing virtually impossible to get flush with the floor. I managed to get it in there but there is a gap between it and the floor. The surface of the slab is also quite poor, with divots etc, so my plan was to screed the slab (and pack some concrete under the flashing in the gap), then waterproof afterwards.

    Questions:
    - The plumber has installed 2 control flanges on the floor for the 2 drains. What is the best way to screed around these without tipping concrete down the pipe and ending up with a nice finish?
    - A builder mate of mine said that since this house is a rental, he would recommend putting the waterproofing under the screed, this way if the tenants chip a tile etc, the waterproofing membrane remains in tact. I just cant see how this is physically possible given the condition of the slab. Thoughts?

    Cheers,
    Mrpotatohead
    Waterproofing the base first then screeding would work, it also gives a better seal over the puddle flanges. You can create 'some' fall and fill all the divots at the same time leaving a good finish for waterproofing by using some self leveling compound.

    To prevent screed getting into the drain just stick a bit of pvc pipe the same size down the hole with a joiner inside and no glue, or find jam jar or food tin just a few mm larger.

    Good luck.
    Growing old is compulsory, growing up is not.
    http://www.wet-seal.com.au/waterproofing/locations.html

  3. #3
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    Quote Originally Posted by Oldsaltoz View Post
    Waterproofing the base first then screeding would work, it also gives a better seal over the puddle flanges. You can create 'some' fall and fill all the divots at the same time leaving a good finish for waterproofing by using some self leveling compound.
    Oldsaltoz, thanks for the reply.

    I did consider levelling it out, waterproofing and screeding, but the slab needs to be raised by 10-15mm in some areas just to meet the flashing, and I thought the screed might be getting a bit thin in some areas afterwards.

    In your opinion, what are the chances of tennants chipping a tile? Have you had many jobs with waterproofing fails due to cracked tiles?

    Cheers.

  4. #4
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    Just be aware that not all the waterproofing compound/liquids commonly available are suitable for areas that do not have a gradient to the waste. Some are. Some also require priming. Some don't. So if you are doing a double layered membrane - if the bottom one under the screed does not have a gradient to the waste you will require to shop around accordingly for your membrane system.

    As someone once said - "Picture is worth a thousand words"....

  5. #5
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    Quote Originally Posted by MrPotatohead View Post
    Oldsaltoz, thanks for the reply.

    I did consider levelling it out, waterproofing and screeding, but the slab needs to be raised by 10-15mm in some areas just to meet the flashing, and I thought the screed might be getting a bit thin in some areas afterwards.

    Your right, screed should be at least 25mm thick to avoid cracking and crumbling, however leveling compound can be spread to a just a few mm


    In your opinion, what are the chances of tenants chipping a tile? Have you had many jobs with waterproofing fails due to cracked tiles?

    I would say very slim, I have never seen it in all my years of waterproofing and the oly 'failures' I ever had were 3 leaking screens, sealed by installers and one leak through the grout between the tiles because the tiler tiled over and above the water stop around the shower, he had to the whole thing again..

    Cheers.

    Good luck.
    Growing old is compulsory, growing up is not.
    http://www.wet-seal.com.au/waterproofing/locations.html

  6. #6
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    Thanks for the replies.

    I definitely think its best to screed then waterproof. Now I just need to measure the premade shower, install the waterstops and away I go!

    Cheers.

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