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Why is floor leveling screed mix so dry

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  1. #1
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    Default Why is floor leveling screed mix so dry

    I've just put down the screed on my bathroom reno to give the floor some fall into the floor trap and was wondering why it needs to mixed so dry. What sort of a problem does extra water in the mix cause ? The only thing that I can think of is that less water possibly makes the screed more porous when it has set, so that if the water proofing is under the screed then any water penetrating the grout won't puddle just underneath the tiles. If this is the case then is it ok to lay the screed with more water in the mix and then put the waterproofing on top and then the tiles ? Hope you understand what I'm getting at.

  2. #2
    Tool Whore - 1K Club Member Vernonv's Avatar
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    I think the reason is two-fold - 1. strength and 2.shrinkage.

    1. The greater the water to cement ratio (i.e. the more water) the weaker the resulting screed will be.

    2. The more water in the mix, the more shrinkage you get. The more shrinkage you get the more likely it is to crack and possibly separate from the underlying substrate.
    Cheers.

    Vernon.
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  3. #3
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    When doing a complicated fall it makes it alot easier to shape, you can't really shave back the mix when it is wet, when dry it is also going to hold it's shape as there is no viscosity to it and isn't affected by gravity. As well as what Vernon said, concrete is strongest when it is made with the minimum amount of water needed to set of the chemical reaction.

  4. #4
    1K Club Member arms's Avatar
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    screed bed is just moist so that it can be profiled to fall to drain ,if its too wet all it will want to do is level itself ,wet mix doesnt matter on level floor but on contoured floor can be a real pain when it moves from where you put it
    kind regards
    tom armstrong
    www.kitcheninabox.com.au
    Flat Packed kitchens to the world

  5. #5
    Old Chippy 6K
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  6. #6
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    Default

    Thanks for the replies, tiles (black porcelain) are down, looks good.


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