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Thread: waterproofing before tile

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  1. #1
    DIY Member rrekih's Avatar
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    Default waterproofing before tile

    I am redoing my front porch.
    It is approx. 8ft by 3ft.
    I have put down 3/4in ply. with joists spaced at 14in, the short way.
    I want to put down tile, what is my best way to waterproof the ply. before I lay the tile?
    I have thought of using a membrane type of product.
    Does what you lay have to have some roughness for the mortar to take.

  2. #2
    Plumber jimbo's Avatar
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    Best advice....see our friends on the tile forum, johnbridge.com

    From my personal experience, there are couple of products you might use:

    A few companies make membranes. They are intended and designed for direct application of the tiles. There is also a paint-on coating called RedGard which also works well.

    Most importantly, tile needs to be on a very rigid substrate. Any flex will cause tile cracks. Generally, a 1" minimum thickness of subfloor is recommended.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Look at www.schluter.com for waterproofing. Laticrete and Noble also make some good products. Ditra is an anti-fracture membrane that could be applied to the plywood. Since it comes in 1M wide sheets, you wouldn't need any seams. You'd probably want to use some Kerdiband and waterproof up the house side wall and a drip edge at the outside edges. If there's living space underneath the porch, you should consider other stuff. Schluter makes all of those as well.

    If the tile is natural stone, you need a second layer of ply, at least 3/8", offset from the first layer, otherwise, the 3/4" should be fine for porcelain if the footers are solid and there is adequate support for the outer ledger board.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    FlooringSupply lajoe's Avatar
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    Default waterproof fabric

    Jimbo and jadnashua are completely right read this page and you will have more knowledge of how to install the waterproof fabric, don’t forget the corners that needs special piece.
    http://www.flooringsupplyshop.com/sh...3-sq-1281.html
    http://www.blanke-co.com/index.php?id=435
    and off curs the subfloor ¾” and up. Will do the job

    give us some feedback how it goes


    Jack

  5. #5
    Licensed Building Contractor dtherrien's Avatar
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    rrekih.....install the 1/2" water proof hardi backer board on top of the plywood. I would cement it down with karabond mixed with karalastic with a few screws so it doesnt move. Install your tiles with the same cement of karabond/karalastic......grout with epoxy grout.......make sure you use a good quality tile as this will not come apart easily.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by dtherrien View Post
    rrekih.....install the 1/2" water proof hardi backer board on top of the plywood. I would cement it down with karabond mixed with karalastic with a few screws so it doesnt move. Install your tiles with the same cement of karabond/karalastic......grout with epoxy grout.......make sure you use a good quality tile as this will not come apart easily.
    A common misconception is that stuff like Hardibacker or any cbu is waterproof - WRONG! In this instance you need waterproof to keep the ply intact for the long-term. All cbu's are not damaged by moisture, but that in contact with the ply over time is not a good idea.

    One thing I like about Ditra is that it is waterproof, a great decoupling membrane, and has channels in it that allows the substrate to breath, which is a great side benefit.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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