Bathtub installation -- order of installation (end pony wall, tub, heated floor)?

Discussion in 'Shower & bathtub Forum & Blog' started by jch, Jul 10, 2011.

  1. jch

    jch New Member

    Here is my gutted bathroom. I have a left-hand-drain Kohler Villager cast iron tub (with apron) that I want to install along the far wall (i.e. along the wall that has exposed insulation):

    IMG_1431.jpg

    The tub is 60" long and the available space is 78" (with a downward-sloping ceiling).

    Questions:
    1) Do I install the tub (on a ledger board) *before* building a pony wall along the non-drain end of the tub? Or do I build the short (20" 2x6) pony wall first?

    2) I plan on installing a heated tile floor. Because the room has some funny angles (not visible in the picture), I was going to run my own heating cables and then pour Self-Leveling Cement. Do I run the cables and pour the whole floor *before* installing the tub? Or do I put in the tub first and then pour SLC on the remaining area? (The heating cable would only be under the exposed tiles, not the tub). My concern is the joint between the tub & SLC, and the reduction of tub-height -- it's only 14" to start with.

    This is my first bathroom reno, so I'd appreciate any tips.

    Thanks!
    .../j
    Last edited: Jul 10, 2011
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,038
    Location:
    Bothell, Washington
    Last edited: Jul 10, 2011
  3. jch

    jch New Member

    Thanks for the speedy reply Terry!

    I'm hoping that the concrete won't need to be that thick (for headroom). I was hoping for more like 1/4 - 3/8" thick SLC if possible. Or am I dreaming?

    And does the wooden apron support stick out in front of the apron? Or do you try to install it flush with the front of the apron?

    Thanks!
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,038
    Location:
    Bothell, Washington
    I haven't installed the electric heating mats, but they may go under the tile without doing too much.
    If that is the case, just set the tub on the plywood.

    You only support at the back wall. One stringer does it.
  5. jch

    jch New Member

    The more I think about it, the more I think that I'd better do the SLC last. I *know* I'd end up dropping something on it while wrestling a cast iron tub around the room... :)

    So how does this sound then:
    1) Build 2x6 pony wall along non-drain end of tub
    2) Install wooden 1x4(?) along floor where tub apron will sit
    3) Install 1x4 or 2x4 ledger along wall (depending on clearance of tub), measuring up from top edge of apron support
    4) Skid/rotate tub into place using instructions here: http://www.terrylove.com/forums/showthread.php?33212-Installing-a-Kohler-Villager-Cast-Iron-Tub
    5) Install in-floor heating cable
    6) Pour SLC to bury cable
    7) Install Schluter Ditra anti-fracture membrane on top of SLC with thinset
    8) Install floor tiles

    Sound good??
    Last edited: Jul 10, 2011
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,038
    Location:
    Bothell, Washington
    You have enough room there that you may be able to just slide the tub in.

    But either way, so far, so good. That looks close enough for a plan.
  7. jch

    jch New Member

    Excellent. Thanks!
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,051
    Location:
    New England
    SLC is MUCH easier to get nice and level (with no waves, etc.) if you make it a little thicker than you plan. Also, over a wooden subfloor, you need lath - I'd suggest a plastic lath rather than metal as the metal can mess with the insulation on your heating wires if you step on them before the pour. Depending on the slc chosen, some require 1/2" above the highest point when used over wood...take the longest level you have to determine how level the floor is before calculating how much slc you need. the worst thing is to have too little. Check out www.johnbridge.com and read up on slc use - lots of threads and info in their 'Liberry'. Finally, ensure you get a good coat of the primer for the slc or the whole install will be at risk.
  9. jch

    jch New Member

    Thanks for the tip. I haven't checked out johnbridge lately, so I'll drop by there to refresh my memory.

    The floor is currently within 1/8" of being flat and level. I pulled up the subfloor and planed down the top of the joists in line with a laser.

    The only reason for me using SLC is to bury the heating wire. Perhaps it'd be worth spending the extra for heating mats and using thinset instead??
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,051
    Location:
    New England
    Either will work, but slc over top does make it nice and flat while embedding the heating elements well, optimizing the heat transfer and providing a nice flat surface to tile on.
  11. johnfrwhipple

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

    Messages:
    4,222
    Location:
    North Vancouver, BC
    There are many heating mats that can be used for sure but I'm more of a fan of heating cables.

    The Mats offer up a little extra speed in installation but a cable system offers a direct bond from the top of the levelling compound to the subfloor and does not rely on the manufacture's seaming process of the two sheets. With a mat system you need to work the thin-set into the fleece very well and this can be hard to do well without over watering the thin-set and weakening that product.

    Once the cable heat is installed you might consider a product like Schluter's 'Ditra', Nobel Company's 'Nobel TS' or Mapei's 'Crack and Sound Membrane' over your levelling pour. Remember if you use the Ditra product you will strictly reduce the amount of setting materials available to you. Here in Vancouver the crews I'm working with have been using lots of the Mapei product and many of the setters online have been using Nobel TS. Mostly because they can use the same thin-set to set above and below the membrane.

    If this is your first bathroom renovation you might further consider using a liquid membrane for all these steps including the bathtubs walls. Look at products from Mapei (AquaDefense) and Laticrete (Hydro Ban). Both offer up crack surpression and waterproofing. Much easier to work with than Kerdi.

    Good Luck.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,679
    Location:
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    Installing the bathtub will be MUCH easier if it is done BEFORE the pony wall is constructed.
  13. jch

    jch New Member

    I'm looking at using the NuHeat Solo/220 wall controller (because it seems easy to program without digging out a manual each time). Is there a type of compatible heating cable you'd recommend? I was thinking of using TrueComfort because of the floor attachments and easy availability...

    The original plan was to lay down:
    3/4" ply with no underlay
    SLC primer
    Heating cables
    SLC primer
    SLC
    Ditra
    Porcelain Tiles

    Do I need underlayment if I use the SLC primer directly on the plywood? Or would underlayment mean that I could do without the plastic lathe in the SLC??

    Interesting. My neighbour's son (a tile setter for 25+ years) swears by RedGuard. Maybe it's the heavy Mike Holmes/Schluter PR, but I'm having a hard time trusting that a rubbery paint-on membrane won't dry out/crack over the years... (Actually, that I'd be able to install it so that it wouldn't crack..)

    I've already bought a Schluter shower kit (pan, curb, drain, Kerdi) to use in the *other* bathroom reno in the house so I'm gonna have to learn how to use it/curse it at some point :) I'll definitely consider using a paint-on membrane on the first one.

    Thanks!
  14. jch

    jch New Member

    Would you recommend connecting the drains before building the pony wall? I have access from the bathroom underneath (it's all bare joists baby!).
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,051
    Location:
    New England
    It's always easiest to install the drains when you have easy access. It can be done either way, but afterwards requires more skill.

    Ditra has a minimum tile size (2"). This is to ensure that enough of the tile is supported by pillars of thinset around the waffles so it won't cock if stepped on with a high load point source. Other than that, it's pretty easy to use. Some thinset manufacturers sell a decent unmodified and you can mix it either with water (and maintain the unmodified characteristics), or mix it with their addative, and that makes it a modified thinset (rather than buying a modified at the plant that you then mix only with water). Done this way, you don't need two different thinsets, just depends on how you mix it up. Because of the waffles in Ditra, the amount of actual thinset used may end up less than with a plain membrane - painted on or embedded.

    The critical thing with Kerdi is mixing the thinset properly and using a quality product. Second, getting it up before the thinset skins over. embedding is really pretty easy once you get the hang of it if the thinset is done right. If you can find it, DitraSet is a really nice, creamy thinset made for Schluter. The key to proper thinset mixing is the right mix, the right paddle, and mixing it long enough. Using a timer helps. most people don't mix their thinset per the manufacturer's instructions. The difference in texture can be quite dramatic - those extra minute(s) really make a difference. Some people compensate by adding extra water. this is often unnecessary, and weakens the thinset, if the proper mixing is done.

    A manufacturer's rep told this story to us in a class. they had a pro complain about the texture of one of their thinsets. The pro watched as the guy mixed up a batch. Knowing it would be hard to change the guy's mind, they said let us research it. They came back a few weeks later and told him they had some new stuff for him to try. The guy mixed it up the way he usually did, and the tech said...keep mixing. this went on for a couple of iterations. Then, after the manufacturer's mixing time had been used, he told the guy that's good. The guy then commented that the stuff was MUCH better. Then, the rep told him that it was exactly the same thinset...just that it had been mixed per instructions.

    The gotcha with paint on membranes is achieving the required thickness. Most people have a difficult time actually getting it thick enough, and pinholes are a potential problem as well. Get it too thick and you've spent a bunch more in materials and time than needed. Too thin, and it won't do the proper job.
  16. jch

    jch New Member

    Roger! I'm planning on using 12" x 24" Porcelain tiles, so the bigger problem will be floor flatness... Not sure whether my thinset workmanship will be good enough to get these tiles in-plane with each other....

    Any ideas about the questions raised in post #13 (above)?? (Heating wire compatibility, underlayment requirements, lathe requirements)
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,051
    Location:
    New England
    All of the slc installation instructions I've read (and there are some new ones out there I've not read up on) require lath on a wooden subfloor. Ardex has a new one that might not. On large format tile, you may want to look into something like the Tuscan Leveling System or the QEP system (cheaper, since you don't have to buy a special tool and available, here at least, in HD). These utilize a t-shaped strap and a break off bracket to hold the tile in plane while the thinset cures, then you break them off (they break off below the tile) and then grout. On any large format tile like that, you want to burn a thin coating of thinset on the backs prior to setting them (use the flat side of the trowel and really push the thinset into the tile). Done right, the thinset gets pushed into the small pores of the tile, and radically inmproves the bond strength. If you don't push it in enough, the thinset can just roll around on the back of a good porcelain. Flat is critical when using large format tile...even a pro gets slowed down when the prep work is marginal on a wavy floor.
  18. jch

    jch New Member

    Thanks! Given that large-format tiles are so demanding in terms of flatness, perhaps I should defer buying the tiles until I see how flat of a pour I can do myself.... I could get lucky.

    There's a pro tile supply place in town here. I'll go down and read the instructions/requirements on some SLC bags there so I won't have to keep pestering you fine folk with newbie questions. :)
  19. Obama the Plumber

    Obama the Plumber Plumber

    Messages:
    47
    Location:
    Washington DC
    Make sure when you install the tub drain, that you don't put anything on the threads of the lower drain fitting. That works by clamping the metal threaded drain with the lower shoe, and sandwiching the tub and rubber washer in between.

    You can put putty under the flange, that is between the tub and metal drain.
    Below the tub, is the rubber washer and then right below that the shoe which receives the threaded drain from above.

    The drain would seal even without the putty if it's threaded up snug and tight.

    The other day I say someone put Teflon tape on the threads, and it prevented the drain from threading down completely and "clamping" the tub. I had to remove everything, pull off the tape, clean things up and then thread it down until it clamped. Even when I explained why I was doing it that way, the response I got was, "It should have worked"
    No, It in fact does not work! He had so much tape on the threads that there was a gap below the tub of over a 1/4". The drain had bottomed out with all the tape and it was stuck before it could clamp the rubber washer against the bottom of the tub. Needless to say, there was plenty of water dribbling downstairs before it was fixed.

    Here's a big clue guys. Teflon tape can only be used on tapered threads.
    That would be places like shower arms
    Nipples that thread into a female IP fitting.

    Places you can't use tape:
    compression fittings
    Flex connectors, (they have rubber seals on the ends)
    Flexible lav supplies (they have seals on the ends)

    So.....get it right, or I will make it right for you.

    [​IMG]

    All this gooey Silcone dripped everywhere and it was a horrible leak.
    Last edited by a moderator: Aug 6, 2011
  20. jch

    jch New Member

    How do you folks recommend getting a SLC install flat enough to install 12x24" tiles??

    I was considering putting a skinny (1" wide?) 1/2" thick plywood strip around the outside of the room to rest a screed on. Remember, I'm going to install heating wires and plastic lath first.

    Would the 1/2" plywood strip help me make the SLC more level? Would it interfere with the expansion/contraction of the SLC when the heat is on?

    Suggestions?? Thanks!
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