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Raising bathroom floor

smokey059 | Posted in General Questions on

I’m building a small apartment on a slab on grade concrete floor. I’m going to use wood flooring thru out the space except for the small bathroom (65sf).  I’m going to follow the subfloor install similar to the link provided. Two layers of plywood floated over the concrete slab and maybe a layer of foam below the plywood.(haven’t decided) then wood flooring.

My question is could l do that same subfloor in the bathroom even though that will be tiled.  I’m thinking tile can’t go over something floating. If not how can I raise the bathroom floor to the same height as the rest of the apartment and have it  acceptable for tile to be installed? How about sleepers screwed to the concrete with a layer of plywood over it for the bathroom area?
Also do you think I should put the subfloor (not hardwood flooring though) down first before the sheetrock  goes on the wall studs or sheetrock  first on wall studs then subfloor plywood ?

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  1. patrick1 | | #1

    I had this exact same question when finishing my basement. For most of the basement, we installed Delta-FL dimpled plastic, followed by 1" rigid foam, then OSB subfloor, and finally vinyl plank flooring. In hindsight, I wish I had gone with a vapour permeable flooring but the rest of the setup is considered best practice (see here):

    With that setup, the finished floor was about 1 3/4" off the concrete and I wondered about how to raise the tiled bathroom floor. I looked on a number of forums and the answer I got was that you can't confidently use the same subfloor setup without risking cracked tiles or grout...too much potential for movement.

    The only solution that would come with a warranty was to use 1.5" thick Wedi board as a substrate for tile. These simply get set in thinset mortar directly on the concrete and then you can tile right on top of it (after following all their waterproofing steps). It was a bit more expensive than other options (e.g., Schluter products) but it dealt with the height issue and also has the advantage of giving us R5 insulation under the tile, consistent with the rest of the basement floor. The other great feature was that the 1.5" Wedi board mates perfectly with their shower pans so we were able to easily do a curbless shower.

    I think I still have some pictures of when the tile guy was installing the Wedi. I'll try to dig them out and post them along with some pics of the transition at the bathroom entrance.


  2. tommay | | #2

    Why not just use a bonding agent and pour some concrete to whatever level you need?

    1. patrick1 | | #3

      Yeah that was an option I forgot to mention. Or you could also do a mud base to get the tile up to the right height...basically the same approach. In my case, I was trying to avoid a cold floor so I wanted to get some rigid foam under the tile (Wedi has a rigid foam core). Concrete or mud base would work but you would have a cold floor without some kind of in floor heating. R5 actually makes a noticeable difference.

    2. smokey059 | | #4

      Thanks for the info on the wedi. Ill look into that.
      I too would rather have something that takes some of the cold off the tile. I did look into schulter products for the shower but never looked to see if they had anything that thick like u say wedi has 1.5". That would be the right height to match the wood flooring for the rest of the apartment floor. How long have u had the wedi down? Any issues with the tiles over it now? Do u like your curbless? any problems with water getting out the shower and onto the bathroom floor? Do you also have a drain on the bathroom floor? I've considered curbless but don't have a drain outside the shower door. If u find the pics I'd like to see them if you don't mind posting them. Thanks

      1. patrick1 | | #5

        We've had the wedi installed for about 10 months now. Everything works problems at all. Wedi is really a high quality product. It's quite a bit more rigid than competing products because the foam is sandwiched between two layers of a cementitious coating reinforced with fiberglass mesh. Also, the fluid applied Wedi seam sealant has some advantages over a tape set in thinset mortar, namely less buildup and no possibility for water to wick through the thinset. If you get the wedi installed by a certified installer, they back it with a 20 year warranty.

        The curbless shower has enough slope that the water is really well contained. Also, our shower glass extends right to the tile so that also really helps to contain the water. It wouldn't really matter though because the wedi board (with correct sealing procedures) makes the entire bathroom floor waterproof. If we had put wedi board on all the walls (instead of just the shower walls) we probably could have omitted the glass altogether and just had a wet bathroom, but we didn't know how well the the shower pan would contain the water so we erred on the side of safety.

        I've attached a few pics. We ended up with a slight transition down from the tile to the laminate because the concrete needed to be leveled with self-leveling compound, which added a bit of height.

        1. patrick1 | | #6

          You'll need to tilt your head to the left for the first 3 pics...sorry about that. They were oriented the correct way on my computer...not sure what happened there.

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