Bathtub Support / Leveling

Discussion in 'Shower & Bathtub Forum & Blog' started by jrmorton, Nov 24, 2011.

  1. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Hi Everyone,

    I am installing a new bathtub and am trying to ensure it's properly supported and leveled. I am installing an American Standard Princeton tub with an apron. My flooring is down to only the rough 1x6" plank subfloor. The flooring is slightly out of level (maybe 3/8") from end to end. The flooring is also generally uneven between planks. The instructions state that a support stringer 2x4 should be installed, and that a mortar bed should NOT be used. I am concerned that if the floor is not level, and the support stringer is, that the tub will not be properly seated/supported on the floor.

    1) Should I install an underlayment under the bathtub to provide an even surface for it to sit? If so, would 15/32" BC pine plywood be an OK choice?

    2) It was suggested to me to try to layer tarpaper under the tub to level the flooring where needed. Does anyone here think this would work, or does anyone have another suggestion for how to level the floor in my scenario?

    Thanks,
    Dave
  2. Maintenancemouse

    Maintenancemouse New Member

    Messages:
    4
    Location:
    Maryland
    Good question Dave!

    I had a similar issue when I thought my tub rocking was due a poor install of the stringers. So in the mist of trouble shooting my tub wiggle, I knocked down the stringers down a 1/4". Wasn't the issue, I found a bulge in the floor. To solve this I laid cement board under the tub area and followed with self leveling cement. My new installation of the tub went with no wiggle, so i hooked up the drain and overflow tube.... but i forgot to raise the stringer.

    so like you, in the sense, I wonder what's more important. A level base or stringers?
  3. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Thank you for the suggestion. I had read about SLC when trying to find a solution, but was concerned about being able to limit the area in which it would be applied. For example, how do you keep it from falling through the cutout for the drain? I also wouldn't want it seeping out the sides of the tub area and through the subfloor, etc. How did you tackle that? It seems when I find examples of SLC online, the scenarios seem more straight-forward than what I'm working with :)
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,259
    Location:
    Land of Cheese
    You might consider what you are doing with the bathroom floor as a whole. You cannot lay most types of bathroom flooring on top of a plank subfloor, it will need to have plywood put down over it. Normally a tub would be set right before the finished flooring material is installed. If the bathroom floor is not flat, the time while the tub is removed is the only good time to fix it.

    As for the SLC, it is pretty easy to make dams with strips of wood sealed with caulk to keep it from going places you don't want it to. Make sure you follow the instructions. Thin pours of 1/2" or less do not usually end with good results.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    SLC tends to be more like pancake batter than water, so thicker is easier to get a nice result. ANd, many require at LEAST 1/2" when applied directly over ply, and you need the primer and lath. You can feather it over a slab or other cement layers (like cbu), but it isn't the easiest thing to feather until you get the hang of it, and some start to set in 10-minutes or less, so there's not much time (that's from the time it first hits water, and some of that needs time to mix it properly).
  6. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Thanks guys, this is great information.

    I think I will try the SLC approach per your suggestions. If i use wood strips w/ caulk for the edges, is it possible to remove the strips that serve as dams afterward? Should I allow the SLC to adhere to the side of my bathroom floor tile, or should I separate it with a strip? I like the idea of being able to easily remove the plywood/SLC if needed, but don't know if that makes it less stable if it isn't butting up against any surfaces on the sides.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    It's suggested that you use something like seam seal or foam insluation strips to give a little expansion room at edges (up against some other fixed object). If the ply and floor aren't anchored and can flex, the SLC may crack and delaminate.
  8. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Thanks for the information and tips. I was going to go the SLC route but I ran into a snag. After putting down 1/2" plywood over my plank subfloor, I am left with a roughly 5/8" recess relative to my tile flooring. There is one problematic corner that is about 3/8" higher than the other corners, making it recessed by only 1/4" below the tile flooring. If I need at least a 1/2" pour, I'll need to elevate the recess higher than the tile floor which won't really work.

    Anyone have any suggestions on how to get this floor level in this case?
  9. Terry

    Terry Administrator Staff Member

    Messages:
    15,289
    Location:
    Bothell, Washington
    Unless you are fixing the entire floor, you will need to shim the tub to level.
    If you are replacing the floor system, you can also figure out a way of shimming the underlayment to bring that to level too.

    If I'm not replacing the floor, I install a ledger board on the back wall set to level, drop the tub on that, and shim the high corner of the apron.
    The new flooring can then go up to the tub, and hide the difference in heights if the bottom edge of the apron is a little lower.

    The piping on the new tub shower valve will need full size pipe to the tub spout.
  10. johnfrwhipple

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

    Messages:
    4,696
    Location:
    North Vancouver, BC
    CAn you post a picture or three? Your floor sounds out of wack and working with old Ship lap floors often the shiplap has dried and curled. Did you pound down the original ship lap?

    How did you attach the plywood over top?

    If the shiplap is sound and the plywood sound to that you can safely start working from there.

    That is a lot of what if's.

    Mapecem Fast Setting Screed Mortar is spec'd from a 1/4" to 2" in repairs and easy to work with.

    Best you post some pictures as I feel there is something more to this install that where missing.

    JW
    Last edited: Nov 28, 2011
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    Didn't find that specific Screed Mortar by that name on the Mapei site, but the Mapei Screed mortars I did find are only designed for installation over concrete surfaces. Some CBU would qualify, but some won't. Depending on the type chosen, they can be applied as thin as 1/16". http://www.mapei.com/CA-EN/products-line.asp?IDTipo=201&IDLinea=101
  12. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    I think I may have overcomplicated the issue by having assumed that I needed to level my floor. My assumption was based on the belief that I needed to support/level the base of the tub, and I have since come to realize that the tub base on this model does not need to contact the floor for proper installation. My ledger board is level, so that really only leaves the apron that I need to worry about rather than the flooring under the tub. I hope I can simply shim the apron, as Terry suggested, and call it a day rather than worry about the entire floor. The rest of the bathroom flooring is relatively level, so my goal is really only to get the tub installed and level.

    The old tub, which was installed before I owned the home, was not level. The old ledger board was not level and I believe it may have been installed too high. I am including a photo taken immediately after the old tub was removed. I have since replaced the ledger board, taken out the drywall, and put down new 1/2" plywood over the planks. I didn't do anything to the planks, but they seemed sturdy/stable, though generally uneven. I stapled the plywood to the flooring. The shape of the plywood seems to have inherited some of the uneveness of the planks, but it is at least well-secured so that it does not bend/shift, etc.

    Do you all think I can simply install the tub over the plywood, shim the apron, and proceed from there?

    Thanks!

    floor.jpg
  13. johnfrwhipple

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

    Messages:
    4,696
    Location:
    North Vancouver, BC
    http://www.americanstandard-us.com/assets/documents/amstd/install/Install_1011.pdf

    I looked up your spec while having lunch and have not seen a tub that sits on the apron before. The installation guidelines say it does not need to touch the subfloor but I might call the tech department to see if it can. If so a mortar bed underneath would make setting the tub easier.

    If there is room in the back side of the front apron for a mini curb it might be possible to set the tub level with shims and then pack in cement product to pick up the weight on the front side. Remember that if the floor flexes and you have the tile touching the tub you could get squeaking after the install. I would use some sill gasket or such as a temporary bond breaker from your tile floor and the apron face if it is going to slip below the tile floor height.

    Wish I had first hand expierence on this model for you.

    I also don't like the roofing nails that tight to the tub as shown in the diagram. I prefer a little space so there is some room for expansion. a few layers of electrical tap will give you a little space between the nail and the tub.

    JW
  14. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Thanks for the response, John. These instructions you found, from what I can recall, are nearly identical to what shipped in the box for my 2390 model of this tub. The instructions did not mention a mortar bed, but I found an alternate version of the instructions on American Standard's website for the same model I have. Those instructions add that a mortar bed is acceptable for my tub. The way that things will work out after I shim, is that the base will be raised slightly off of the plywood. I plan to include a mortar bed into the installation so that the base is set in the bed.

    Just so that I understand you correctly regarding your suggestion to pack in cement product, are you referring to filling the gap that would present itself under the apron between the high side of the tub and the shimmed low side? Is the intent to allow even distribution of the weight along the apron rather than at the ends?

    Thank you as well for the suggestions regarding the nails at the flange and the sill gasket. I will include that in my installation.
  15. johnfrwhipple

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

    Messages:
    4,696
    Location:
    North Vancouver, BC
    I would set it up so you get good coverage under the tub bottom itself. We like to use 6 mil poly as a bond breaker between the tub and the subfloor.

    I would set it up with a couple of shims on the apron side so once you press the tub into position it can't go any lower. This might be difficult depending on the tub's relation to the tiled floor. Often a tub will have a few inches of clearance between the tubs bottom and the subfloor. You can infill this area with a little scrap plywood and leave some room for the mortar mix to fill. With a couple bags mixed up you can place this in the center of the area and then drop your tub down. If your shims are right and the ledger board good you can wiggle the tub right into position.

    Once set you can the next day pack in more mortar under the apron to infill some more. I would imagine that apron has a good 3/4" of width to it.

    The poly as a bond breaker will allow you if need be to remove and replace the tub for what ever reason.

    Do you have access to hook up the tub's overflow and waste from the side or do you have to work entirely from above? Much easier not to have to do it this way.

    Do you have solid blocking around the perimeter of the tub's tile flange? This makes for a solid install and offers up the best protection from leaks at this point.

    What about a shampoo niche?

    What about grab bars one day?

    Backing for the slide bar?

    Backing for the towel rods?

    Get all this in place while you are in framing mode.

    JW
  16. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    Thank you for the detail, John. That makes sense. I shimmed everything as discussed and the tub is now level! It's loose in there right now, but I am aiming to complete the installation today. Luckily I do have easy access to the tub's overflow/waste from the adjacent closet and from the basement. I think I should be good with supports for accessories/attachments but I am going to double check, thanks for reminding me about that.

    Also, thank you everyone else for taking the time to help me out. I'm learning a lot and am appreciative of you all steering me in the right direction.

    Dave
  17. johnfrwhipple

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

    Messages:
    4,696
    Location:
    North Vancouver, BC
    Thanks for the kind words Dave.

    I'm always impressed with the quality of work produced by avid DIYer's. Every month here in Vancouver we help some new client execute their renovation. More and more of my clients just want us in to waterproof and flood test and then they take it from there. Your attention to detail and research should be practiced by more tradesmen and DIYer's alike.

    I hope your renovation turns out just the way you like.

    Have you done a tile layout yet?

    Often we do this before the final framing is set so we can position our shampoo niches at a grout joint.

    Looking forward to the progress pictures - please share them as you go.
  18. jrmorton

    jrmorton New Member

    Messages:
    14
    Location:
    Detroit, MI
    The tub is installed and level! I'm really glad I did the mortar bed too. The tub that was previously installed didn't have one. It's really interesting how noticeable the difference is when you step inside.

    Now I'll be working on a plan for the accessories and tile before I put up the waterproofing/cement board. I hope to have some progress photos soon!
  19. johnfrwhipple

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

    Messages:
    4,696
    Location:
    North Vancouver, BC
    Nice work!

    I stopped by a current jobsite today and the plumber had set the soaker Jaccuzzi tub. Here is a picture underneath.

    The only thing we do different is use poly as a bond breaker. But this should give a little insight into the process.

    [​IMG]

    [​IMG]

    [​IMG]

    JW
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