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  1. #1
    Join Date
    Mar 2012
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    11

    Default Re-doing the floor from the joists up

    1929 Colonial with the original marble tiles/mesh/mortar base in the only full bath. The project this summer is to remove all of it and start fresh.

    The issue, per se: perpendicularly, on top of the joists, the builder laid 3/4" pine, then the mortar/mesh and tiles. That combo extends only 2" or so under the facing edge of the tub. To support the body of the old tub, he laid 2x4s across the joists. Okay, doesn't sound great, but it's held up so far!

    My question(s)- after I pull the old flooring and sister up the joists to get them higher/closer to the proper level, what's the proper procedure? I know to lay 3/4" plywood and I know I need backer board. But I've read that I need a waterproof membrane OR visqueenon top of the plywood. Which one?

    I've read that I should adhere the backerboard with mortar OR screws/nails. Which?

    Finally, since I have to pull the tub, should I tile under it, too? It's more work, but I guess I'm worried about watertight integrity.

    Any help is greatly appreciated, since my lovely spouse thinks I know everything...

  2. #2
    Join Date
    Jan 2010
    Location
    Northern Virginia
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    1,146

    Default Re: Re-doing the floor from the joists up

    I would use 3/4" ply (with panel adhesive and nails), then 1/2" ply, staggering the joints of the 3/4 but still breaking on the joists (use screws).
    Then use Schluter Ditra mat (waterproof) and then your tile. I avoid cement board, it adds no rigidity to the system and is not waterproof. The 1/2" ply at least adds some substance. The more plies your plywood has, the better/sturdier it is.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  3. #3
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,942

    Default Re: Re-doing the floor from the joists up

    Chip,

    The first thing to do is determine if the joists are adequate for tiling. Just because there was tile before, doesn't mean the new plywood over the joists will work. The John Bridge Tile forum has a 'deflecto-meter' you can use to determine what the joists need if anything. Joist spacing as also another issue which effects plywood thickness. We don't know your joist spacing.

    If you are using natural stone tiles such as marble, then you'll need 1.25" of plywood, usually in 2 layers set in a specific method.

    Ditra is a great product and can be used to waterproof a bath floor when installed for that purpose. Ditra does require a tile no smaller than 2", so if you are going to restore the floor using smaller tiles, then another waterproofing would be in order. There are choices.

    Your best bet is to head on over to the John Bridge forum. There you will find Pro's who are well versed in all phases of bathroom remodeling, plus posting pictures is a lot easier there. Tell them Houston sent you.

  4. #4
    Join Date
    Mar 2012
    Posts
    11

    Default Re: Re-doing the floor from the joists up

    Thanks for the quick responses. The joist spacing is 16" o.c. and I have to add at least 2x6s to raise the level. As I'd written, the bathroom floor 'base', if you will, is lower then the surrounding flooring. The builder 'raised' it to the same height by adding the mortar bed/tile.

    Our tile selection is an American Olean unglazed porcelain, 12x12 sheets with 1 1/4" tiles.

    Any suggestion on whether I should tile the entire floor before replacing the tub? It'll be the same one, since it's an odd size that would cost way too much to replace.

  5. #5
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    1,146

    Default Re: Re-doing the floor from the joists up

    Hi,
    When I was doing my own bathroom floor with small marble mosaic, I got the advice of a tile guy who has been through the Schluter school and has used their system for over 5 years and he has done a lot of bathrooms for us; he advised me that it was fine to use < 2" tiles on the Ditra, provided that I carefully pre-filled the grids with thinset. I did, and no problems after 3.5 years use. The smallest "tiles" are the 3/8" square dots in the basketweave.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  6. #6
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,710

    Default Re: Re-doing the floor from the joists up

    It sounds to me like you have a classic and elegant floor now. Why do you want to replace it?

  7. #7
    Join Date
    Mar 2012
    Posts
    11

    Default Re: Re-doing the floor from the joists up

    Keith, I'm sure it was "classic and elegant" when it was new. Sadly, it now has long, meandering cracks, has settled unevenly in some spots and is impossible to clean. Also, several years ago we gutted the walls to studs - since the original pink () tile was set in mortar/mesh, we ended up with about a 1" gap at the perimeter. As a temporary fix I filled it with grout and now we just can't stand that contrasting stripe!

  8. #8
    Join Date
    Mar 2012
    Posts
    11

    Default Re: Re-doing the floor from the joists up

    Gawd, I love the 'net! Okay, I'm looking for some BTDT info: the suggestion for Ditra mat has me 99.9% certain that I'll be using it. But has anyone used the Kerdi membrane? The Schluter website indicates that plain, old drywall is an acceptable substrate in the tub surround, and given the existing arched ceiling I'm looking for an easier way to button that up.

    My concern is that we have glass mosaic tile for the ceiling: I need to know that I'm choosing the right product to install it. The walls will be standard 8x10 porcelain.

    Any input?

  9. #9
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    1,146

    Default Re: Re-doing the floor from the joists up

    My previously-mentioned tile guy who turned me on to the world of Schluter, does the sheetrock+kerdi deal. And he gets good results. For me, in my on house, I was too chicken, so I stayed with Durock and then Kerdi over it. I really worry about a tub surround in drywall, because the bottom seam is very problematic/vulnerable. However, I would be willing at some future time to try the 1/2" Kerdi-board, which was not available at the time (In 07) when I did my bathroom. It seems like a winner all around.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  10. #10
    Join Date
    Mar 2012
    Posts
    11

    Default Re: Re-doing the floor from the joists up

    Redacted - realized it was a dumb question.
    Last edited by chipset; 07-08-2012 at 07:27 AM.

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