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  1. #1
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    May 2011
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    Default What thickness should the subfloor be if you are planning on a tile floor?

    I have removed a vinyl half bathroom floor down to the 1x6 floor boards on the joists and want to install a floor of either ceramic, porcelin or stone tiles. Do I put 1/4 plywood on top of these board, or 3/4 in plywood to create my subfloor?

  2. #2
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    nova scotia, canada
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    for the houses i renovate i dont install anything less than an overall thickness of 1- 1/8", this is the combination of floor sheathing and underlay

    new construction used 3/4 " t&g plywood or osb and 3/8 underlay. In older homes such as yours where there are t&g boards used you will need the underlay to be slightly thicker. my tile guy will not warrenty a floor he tiles over boards unless we use anything less than 1/2" plywood glued and nailed using construction adhesive and ring nails. the boards alone arent as strong or stable as plywood so using 1/2" will lock the floor together much better making it stronger and create a flatter surface to tile over
    fire up the saw and make some dust

  3. #3
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    According to the 2011 TCNA guidelines, you'd want no less than 1/2" plywood over that floor, properly attached to the joists only. Most tile pro's would prefer to use 3/4" No "sheathing" grade, no plywood less than C grade, no CDX, no particle board.

    Once that is down, spread thinset under your 1/4" cbu which then gets screwed down or nailed with ring shanked nails.

    Have you checked the joists to see if they can handle a tiled floor? The joists can have a deflection no less than L360 for ceramic tile, or no less than L720 for natural stone. The John Bridge Tile forum has a deflecto-meter you can use to see if your joist structure can handle a tiled floor.

    Natural stone also requires at least 1.25" of plywood, normally achieved in 2 layers. The planking doesn't count towards the thickness for natural stone.

  4. #4
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    florida
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    [QUOTE=HoustonRemodeler;250690]
    Have you checked the joists to see if they can handle a tiled floor?
    QUOTE]

    HoustonR's ? is the 1st thing that needs to be answered.

    I would look at the thread below SophieC had the same questions......She has done one SWEET A+ job getting her floor up to par..

    https://advice.thisoldhouse.com/showthread.php?t=117832
    Gizmo

    Cut it 3 times & it's still to short.
    Inventor of the Miter Master Plus.

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  5. #5
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    nestor yet again you prove yourself to not know anything about what your talking about. why do you continue to question the practices of tradesman that work in the high end sector of home construction and renovation..

    i have seen int countless times where using the thinnest possible underlay over boards and the tiles have popped, how have i seen this because the first guy messes up then we get called in to redo it the correct way..

    the whole point of gluing and using ring nails is to make the floor as stable as a rock.. any movement in the substrate will either pop the tiles or the grout will crack..

    not only am i a licensed carpenter who has built a reputation for a high level of craftsmanship but also for doing things that last. i am also a moderator here and your very close to getting banned. this is not a threat its your final warning
    fire up the saw and make some dust

  6. #6
    Join Date
    Jan 2010
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    Northern Virginia
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    We prefer a subfloor of 3/4" plus a layer of 1/2" with the joints offset. Then the Ditra; we use Schluter system underlayments/isolation membrane.
    Nothing will help you if the joists have too much deflection; achieving a deflection of 1/720 is the first task for a successful large-format tile floor job.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  7. #7
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    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    casey, you got my vote!!

    doin it the right way, keep er up buddy
    fire up the saw and make some dust

  8. #8
    Join Date
    Jan 2011
    Posts
    93

    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    Quote Originally Posted by hilltc View Post
    I have removed a vinyl half bathroom floor down to the 1x6 floor boards on the joists and want to install a floor of either ceramic, porcelin or stone tiles. Do I put 1/4 plywood on top of these board, or 3/4 in plywood to create my subfloor?

    hilltc,

    Without knowing the grade, size and condition of the floor joists I could not conclusively determine what is required.

    As a professional, I would have to remove the entire sub-floor (yes that means the 1x6 boards must go) inspect the joists, repair/replace/support as necessary. From this point on the target finish floor height would be an element to consider on what direction I would take to install the floor. This includes sub-floor thickness.


    But, in the real world you are not experienced in the many methods, not going to hire a professional and probably just need to get this done without all the tech stuff. So inspect the 1x6 boards, reattach/re-fasten where necessary, install 3/4" A/C ply with lots of PL Premium glue and 1-1/2" screws min every 6". Use a high quality modified thinset right over the plywood such as tec SuperFlex and you're done.

  9. #9
    Join Date
    Jun 2007
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    Fayette County, Ohio
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    5,557

    Default Re: What thickness should the subfloor be if you are planning on a tile floor?

    Quote Originally Posted by Nestor View Post
    This is a homeowner who's new to floor tiling. Lots of things can go wrong, and the job might end up being a total disaster.
    that option open to him.



    So, how close am I now to getting banned?
    One way to insure that things can go wrong is by not installing a soild base. And to answer your quetion, very close.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #10
    Join Date
    Mar 2008
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    Wink Re: What thickness should the subfloor be if you are planning on a tile floor?

    Lihr, you got the job

    good man i like your way of building. the only issue that should arise with the floor built this way is if the homeowner decides 6 months later they dont like the color of the tile they wont want to take it up because its built so well.

    rock on brother and keep that circ saw singing
    fire up the saw and make some dust

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