I shouldn't even have to put this up as a thread

Discussion in 'Toilet Forum discussions' started by Dunbar Plumbing, Mar 21, 2009.

  1. But here it goes.

    I've always been told that on tile floors, you must have 1" solid wood underneath it, and doing a 1/2" osb floor with 3/8" or 1/2" durarock or schleuter sp? board is not a qualification.

    I have a toilet job I'm doing tuesday and I was going to make sure there's 1" of wood under this toilet or at least set it up so the tile guy doesn't have to pull the toilet, rework anything that I touch at that point, with exception of running the tile up to the flange that will be gauged and set according to industry standard.

    What's going on is I'm probably overthinking this and need to just replace the floor and leave the rest to the tile guy. We'll see.

    I just don't want to get into a predicament where the floor runs to the door with a termination point where the floor got too high, and it is considerably higher than the carpet. That never looks good but I need what's underneath that toilet to be industry standard.

    I'm not a floor guy, I just need specs to make sure this tile and grout never crack due to what's under it.
  2. Cookie

    Cookie .

    Rugged, John Bridge is the tile expert they could probably answer your questions lickety split.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    The thickness of the subfloor is important BETWEEN the joists, and depending on the tile (stone or ceramic) must be strong enough as well as ALONG the joists. Industry standards require a minimum of 5/8" T&G subfloor for ceramic and an L/360 deflection rating. Now, that is for new, undamaged materials. Most people like at least 3/4" (nominal), and more is better. If you have stone tile, things get more stringent. You need a second layer of plywood at least 3/8" thick on top of the first layer, offset from it and properly anchored.

    Then, you need a decoupling layer - personally, I like Ditra from www.schluter.com, but cbu (any brand) 1/4" thick, installed over thinset and then anchored is the way to go. Note, there is an approved method to install tile directly to TWO layers of ply, but the steps to do it and the really expensive modified thinset and no room for errors means most people use a membrane or cbu. There is no big benefit to thicker cbu unless you are trying to match heights. Note, the cbu joints need to be taped with the alkali resistant mesh tape (looks like the stuff for drywall, but isn't...make sure you get the right stuff). You can do this while laying tile to help prevent speed bumps if you try to do it first and it sets up. You're not trying to make a drywall joint, it's to anchor the sheets together and looks don't matter underneath the tile.
  4. Thanks for the responses. I'm going to follow your info on that and talk with the tile guy today and ask him what he wants from me, what he wants me to do and what height he wants the flange.

    I'm literally making this harder than it should be.

    The job I was on last night had cracked grout every in this bathroom and I don't want to be the lead guy who said one thing, and months/years later the inevitable happened.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    The safest thing is to get a copy of the TCNA handbook. (Tile Council North America). They lay out the requirements for tiling not only floors, but wall, and shower construction as well. They're based on the ANSI specs, and form the basis of many codes across the NA continent (well, USA and Canada anyways). They're tested and validated...if you follow the instructions with the proper materials, you can be assured success.

    A big mistake many people make is to not leave a gap around the perimeter of the room or against immovable objects.

    On a new floor, it is far better to install the flange after the tile is in. You must ensure they leave enough room around the pipe to allow gluing the flange in place. If they also notch the tile, you won't have to drill through them to mount the flange, either. this would put the flange exactly where it is supposed to be...resting on the finished floor and anchored through it to the subflooring.
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