Framing for an under mount tub installation

Discussion in 'Shower & Bathtub Forum & Blog' started by johnfrwhipple, Mar 28, 2013.

  1. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    One question that gets asked a lot online is how to "Under Mount" a tub. It's a really good question because there is no real guidelines to follow, at least not from a tile installation point of view. I have been helping out this guy in Ontario (will call him Steve B) with some design ideas for his new bathroom renovation.

    The best advice I can give you is make it TANK LIKE

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    To test my framing on this job I invited the client up on the prep work (prior to stone going in) and we jumped together. The prep work did not butch.

    No movement - no vibration.

    There is roughly a 4.5" set back shown here and a double strip of LED's under the face.
    Last edited: Jul 15, 2014
  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    The hardest part I think for the framing and installation is allowing room for the tub filler and hand held spray hose. Making sure you have room for the hose to retract and not interfere with the plumbing lines is key.

    On my current project we have only a wall hung tub filler and wall mounted flow controls. Easy this way.

    This tub has it's own lighting. Not one of my builds but one I like to show new clients.

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    The tub has I think 4 tub lights. The effect is cool almost uplighting the slate walls...
    Last edited: Jul 15, 2014
  3. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Typically a tub is poorly installed and left on 2"x blocks or plywood.

    If your under-mounting a slab better steps should be taken.

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    This is both an under mount tub build and a floating tub build. A process photo that does not yet show the levelling steps or Ardex 8+9 installation.

    You can see below I stepped back the bottom plate for the reveal...

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    This is some of the prep work for the white stone floating under mount tub in the first picture.
    Last edited: Jul 15, 2014
  4. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    A soaker tub has so much room for water - with this comes so much weight.

    The tub should not compress when filled so bracing the tub from below and the top ois key I think.

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    Of course the lights are a nice touch!
    Last edited: Jul 15, 2014
  5. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    The newest project - July 2014

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    Last edited: Jul 15, 2014
  6. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Hey Vegas - are the switches on these jazzui tubs low voltage? I want to rip out the tub mounted switch and place it on the wall.

    Just wondering if the installation angle might affect some kind of switching mechanism.
  7. hj

    hj Moderator & Master Plumber Staff Member

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    Most of them are "air switches" so there is no "power" by the tub user.
  8. hj

    hj Moderator & Master Plumber Staff Member

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    John; I looks like you are taking over some of these categories.
  9. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Air Switch would be awesome HJ. I'm going to install some Schluter Profile to the edge of the tub deck so when the stone goes over top there is not such a shadow reveal like the last job. I also think the Chrome accent will look sharp.

    What do you mean by "you are taking over some of these categories." ? This will be only my third showcase of the under-mount tub. I have two online clients building their own right now. That makes five total.

    It's a sharp look and makes for a more waterproof install in my book.
  10. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Aire switch for sure. Thanks again HJ. I removed the tub mounted section but the air line was not hooked up at the other end! I hope the job site sparky knows this....

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    Under-Mount Tub Install's air switch - photo source

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    Showing the bevel to the tub deck top - photo source

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    After tile edging is used - photo source

    The four corners will get a radius edge when the stone goes in. The stone or composite slab will overhang this tile edging roughly 1/4"

    [​IMG]

    Later the tub got some 8+9 (two coats). More framing and cement board and then a screed mortar step with some Mapecem Fast Set​
    Last edited: Jul 19, 2014
  11. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    So I did a little more study to how this tub was installed and yesterday I learned as well - AFTER - I did this work that the tub is not even shimmed or supported it four leg locations.


    #$%&* - yet another thing to add to the job list!
  12. eurob

    eurob master tile and stone installer

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    That sucks . I thought you could see it in the photo where the tub is sitting on the 2x4 -- excessive curving -- , but sometimes photos are not reliable . So the outer lip is much higher then the inside one .

    What stone will be installed for this undermount ?
  13. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    I did but when I disconnected the air switch I looked deeper under all the framing to see the plumber used scrap lumber as shims and they do not rest on the tubs four feet locations.

    I'm going to cram in some 4-1 down there in a plastic sandwich. Shove the crap in with a scrap 2"x4"
  14. eurob

    eurob master tile and stone installer

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    I think , if you use something like SikaGrout 212 , it should work .
  15. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    For what? Supporting the tub? What does that cost. I can get six bags of 4-1 for like $30.00 maybe with tax.

    Or pick up some mortar mix for the same price.....

    Later Boys - got to go to work! :(
  16. eurob

    eurob master tile and stone installer

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    So John , what stone will be used ? Marble or granite ?
  17. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Not sure. I'm only prepping the tub for slab. The window for tile. The walls for tile. Setting the ACO drain. Mud bed for tile.

    Noble Seal CIS outside shower.

    New flood test.

    Capillary break.

    And then my part is done.

    Cool home. Has an elevator going in! Nice touch
  18. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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  19. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Another fantastic tub build in the UK.


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  20. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    While John will likely have conniption fits, you could treat the tub like a big undermount sink, make sure to support it properly underneath, and use KerdiBoard for the structure and top and sides. You'd proceed very similar to the way they show building a counter and installing a tiled, undermount sink in this video . You'd get it ready in a fraction of the time, have something that is waterproof, damp-proof, rot-proof, stable, and reliable. If you're paying for labor, far less expensive as well. Or, you could use the more traditional ways and spend more to not get a more reliable result...your choice.
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