Tub on subfloor?

Discussion in 'Shower & bathtub Forum & Blog' started by _mike_, Nov 23, 2012.

  1. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    I'm installing a new bathtub with apron (probably americast), we have a 3/4" subfloor (old tub was installed on that).

    My plan is to add 3/8" underlayment grade plywood, ditra and tile.

    As far as I can tell, I should put the tub in and then butt the 3/8 underlayment to to tub apron and proceed with ditra and tile.

    Is this the best way to approach the job?


    Also, the toilet flange should sit on top of the tile, right? So I should leave the pipe roughed in and cut it flush to the final level of the tile and then install the closet flange after the floor tile work is complete. I have a 3" PVC pipe to work with. My plan is to get a PVC flange that fits over the exterior of the 3" pipe with a metal ring attached. Is that going to produce the best results?


    I've also framed in backing for shower curtain rod mounts to the wall. Is there anything else I should be doing to prep for the tub install?



    Thank you,


    Mike
    Last edited: Nov 23, 2012
  2. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    The floor is ever so slightly out of level. I assume this isn't anything to worry about and even shimming isn't needed. It must be less that 1/8" out over 4' and it's out in the "right" direction. If I put a piece of shingle under the end of the level, the bubble is "off" in the opposite direction.
    level.jpg
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,809
    Location:
    New England
    YOu may want to install blocking for a future (or now) safety grab bar(s). You never know when one is needed. I will say that I just put in one for my mother a few days ago and used WingIts. Really slick, and you specifically don't use them in a stud. But, it's cheaper by far to just screw it into blocking.

    You want the tub to be level, so may need a metal shim to make it so - it needs to be level L-R and F-R.

    You need to make sure you leave enough space around the 3" pipe to glue the new flange on. You do want a flange with a metal ring and it should be on top of the finished floor. Keep in mind that some flanges won't slide down flush, and some will. You need to check how square the top of the flange is both on the inside and outside so it will fit into a narrow slot.
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,770
    Location:
    Bothell, Washington
    Your out of level floor is another reason we use a ledger at the back to support the tub.
    The ledger should be installed with a level, and then the front apron gets shimmed to prevent rocking.

    For the closet flange, I would pick up a spacer and set that under the closet flange, and then tile around that.
  5. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    Thanks for all the info - so the tub goes on the 3/4 subfloor and the 3/8 plywood buts to the the apron right?


    Thank you, good idea. Is there some reference as to where they should be located in reference to the tub? Maybe I'll just install them as part of the job. It seems like a well anchored grab bar would be a good idea no matter what.
    I was unaware I could get a metal shim. Would I go to a plumbing supply store for this and specify the angle I need (1/32" per foot or something like that)?

    No problem there.

    Oh, thanks! I assumed that an outside flange would go down as a far as you wanted, do some have a lip or taper that prevents that? Can I tell from looking at the flange if it's not going to slide as far as I need it to (for example a lip is obvious, a taper, not so much)?

    I'm not picturing this? Is the narrow slot the hole between the floor and the 3" pipe?

    I can ensure that hole is big enough, at the very least I figure I can put a slice in a piece of 4" pvc and slip it over the 3" pipe as a template. The slice is to ensure I can pull it back off.

    The top and bottom of the flange will always be square to the hole for 3" pipe right?

    Or do you mean the flange may taper down to the hole for the 3" pipe and that taper needs to be taken into account?



    Thanks, I understand. Then If I'm going to use motar under the tub, put a bunch of piles down an I should be able to push the tub down to the ledger and and shimmed flange if everything was done correctly.

    That's a great idea - thanks! No worries about breaking the tile when drilling the holes for the flange too. So how would this stack?

    Flange
    Spacer
    3/4" Plywood

    or

    Flange
    Spacer
    3/8" Plywood
    3/4" Plywood
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,770
    Location:
    Bothell, Washington
    Flange
    Spacer
    3/4" Plywood

    The spacer takes the place of the underlayment.

    Tubs are set first, and then the underlayment butts to them.
    Though I've seen them installed on finished floors too. On an uneven floor, that would look odd though.

  7. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    Something as simple as this for shims?:
    [​IMG]

    [ EDIT ]
    I also found some iron on rolls of 3/4" birch edging. This seems better since it can be more easily fixed in place (glue not iron :) and fewer individual pieces would be required because you could just cut long lengths and lay it up as needed.
    [/EDIT]

    How exact do I need to be? For example, I can get a 1/2" spacer locally easily enough. But my buildup is 3/8 + 1/8 (Ditra) + 5/16 (tile) = ~13/16 without taking into account the thickness added by the thinset. Or I can get something like the Set-Rite - Toilet Flange Spacer Kit which provides one each of spacers at 1/8", 1/4",1/2", and 3/4" which seems to be the best way of dialing in the height. As far as I can tell Set-Rite is the only company with such a kit too...
    Last edited: Nov 24, 2012
  8. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,236
    Location:
    Land of Cheese
    I would just set a PVC coupling (dry) over your existing rough-in and install the floor with it sticking up . When the floor is done, pull the coupling off and install the closet flange.
  9. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    Folks who advocate setting the flange "on top of the tile" must not have to deal much with actual tile floors people
    are installing in their bathrooms. While that is the generally correct specification for the preferred height of the
    flange, it is not at all critical, and any method that requires actually drilling holes in the tile for the flange mounting
    is to be avoided like the plague. A plywood spacer of more or less the required thickness is perfectly adequate.

    Moreover, there are large areas of the country that require the toilet flanges to be in place before the rough-in
    plumbing can be inspected, long before any floor finishing materials are applied, or even decided upon.
  10. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    I'm going to try these set-rite spacers if a local supply house has them. Otherwise, I'll make one from plywood. I like not having to deal with drilling the tile and I suspect if I have some plumbing issues down the road that life will be a little easier with additional working room the spacer provide.
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,809
    Location:
    New England
    It's not a big deal to notch the tile prior to setting with the wetsaw, so it's not a big deal especially during a remodel.
  12. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    So because you messed it up the last time you tried means I can't use a tile bit in my drill and be successful...? Wrong.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,809
    Location:
    New England
    With the proper tools, you can cut a nice hole anywhere in a tile without particular worries of cracking things IF the tile is installed properly.
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,258
    Location:
    Cave Creek, Arizona
    quote; Moreover, there are large areas of the country that require the toilet flanges to be in place before the rough-in plumbing can be inspected

    I just slide the flange over the pipe so the inspector is satisfied, they NEVER pull on it to be sure it is glued in place. It also forces the tile people to cut the opening properly, then when I am ready to set the toilet, I pull it off, apply the cement, then push it down TO the floor , cut the extra riser off even with the flange, and set the toilet.
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,809
    Location:
    New England
    A much more civilized, intelligent way to do this. If you need to do a water test, put in a plug.
  16. _mike_

    _mike_ New Member

    Messages:
    14
    Location:
    NJ
    Thanks. I have the flange spacers so now I can do it either way, spacers on the subfloor or on top of tiles. I'll let fear be my guide once I start tiling the floor.

    We took delivery of the tub(American Standard Princeton). The instructions call for a 13 5/8" high 2x4 string across the back wall. I set up a laser level and found the highest 13 5/8" measurement based on all 4 corners of the tub and then used that for my height. It also didn't call for stringers on the two shorts sides, but the old tub had them, so I put put them up to. Is there any reason to NOT have stringers for the front and back as well?

    The plan is to "dry fit" the tub, shim the apron as needed and then for the final install set the tub in a bunch of piles of mortar that will be squeezed down so the tub sits on the strings and apron shims set up during the dry run.

    Here's a photo of the tub stringer with the laser level:

    bath_20121209_17_56_11.jpg
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