(un)Timely tub/shower redo [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-09-2007, 03:32 PM
I've gutted my 1938/1980 main upstairs bathroom to the joists. I'm OK for ceramic tile according to the Deflectometer. Still need to rip up a few of the patched areas of subflooring. After reading and reflecting, here are my most pressing questions: 1. replacing the tub/shower with a new tub/shower in the same position in the alcove. Do I seal the plastic to the tub lip or leave it laying behind the Durock (or whatever you suggest I use)? 2. what kind of insulation do I use? 3. I think Ditra will best isolate any water on the floor--how do you seal the joint between tub and floor/ditra? just use silicone? 4. Should there be 1 more layer of underlayment outside the tub, so the tub is 'sunken' from the floor? And how many layers and what thickness of plywood over the joists? 5. I have to tile the ceiling of the alcove--what do you suggest for backerboard--same as walls? 6. I've been told you can stick just about any vent/light in the tub/shower ceiling...any suggestions of makes--do I have to have a 'wet certified' product? Thanks in advance for your answers, and thanks right now for providing such a forum. It's been a tremendous resource for me.

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Scottish Tile and Stone
03-09-2007, 07:28 PM
Andy, Im a bit confused.

You say to seal the pastic to the tub lip. Do you mean a vapor barrier on the walls?

Are your walls standard 2x4's? Just get insulation for 2x4 walls. I think it should be R12?

Shouldnt have to seal the ditra on the floor to the side of the tub. When you install the tile, the thinset will be right next to the tub.

You shouldnt need anymore plywood unless you need to stiffen the floor, but you already said you meet deflecto requirements.

yes same as walls on ceiling.

Yep you need a vent or light suitable for a wet location..

03-10-2007, 10:46 AM
Thanks for the speedy reply, Scott. Sorry about the confusion--let me clear it up. I'm ready to start rebuilding and need to get my supplies, especially for the subfloor and underlayment (if needed). 1. yes, I meant the 4mil plastic vapor barrier--siliconed to the tub lip --OK. 2. with the vapor barrier, then I use UNFACED insulation, correct? Also , do I vapor barrier on the ceiling? 3. ok 4. i am down to the joists. What is recommended for a. subfloor-- OSB or plywood? (5/8"-3/4" or something like Sturdiwood, if I can find it?) b.underlayment, assuming I use Ditra over it--1/2" plywood enough? 5. just subfloor under tub(porcelain on steel), or subfloor+underlayment? 6. what's easiest/best to use on the walls and ceiling in the tub/shower alcove? Durock or do you suggest something else? Again, thanks...

John Bridge
03-10-2007, 11:28 AM
Hi Andy, Welcome aboard. :)

You don't need to seal the vapor barrier to the tub. Just let it come down all the way and sort of roll onto the tub, hand the backer board and then trim off the excess vapor barrier. You don't want or need it on the ceiling.

If you can't get unfaced insulation, slash the paper face with a rasor blade.

If you want to waterproof the floor, thin set strips of Kerdi-band over the Ditra seams. Use silicone to seal the Ditra to the front of the tub.

03-11-2007, 06:15 AM
Thanks, John for the welcome and the info. I still need some feedback about setting the tub -- on just (new 5/8"-3/4") subfloor, or subfloor+underlayment? Does it make sense to ditra under the tub, maybe then cover with 1/4" CBU or plywood? Pretty nice day today -- and I'll be inside testing the supply lines and starting the subflooring :crazy:

03-26-2007, 02:17 PM
Finally attacked the one weak floor joist in my 6'x10' bathroom. It has a huge notch (for the tub drain) and was half-muled sistered with a few short lengths of 2x4 on top of 2x4s. The joist was so weak the I couldn't just pry the 2x4s out---cut the nails thru with my saw-z. Once the sisters were out I could see a fairly large split through at about half the length of the joist. YIKES. I propose to remedy this by 1. glue/epoxy/clamp joist 2. use matched size 2x8 to sister like crazy 3. block wherever I can, again using 2x8s. My wife used to joke about the floor in the bath being so weak she wouldn't be surprised if someone ended up in the kitchen below. Truth not so far from that--it's almost like the ceiling was supporting the joist. No wonder they had a mud floor in there.
So, please advise if my game plan seems sound...I really don't know what else to do. Perplexed but determined...

05-05-2008, 01:30 PM
It's been over a year and I am finally starting to cross brace my sistered joists. I recall reading in a post a method for cutting cross-blocks accurate to fit between joists...I am having trouble getting a proper fit, i.e. a block that slides in without pounding or gaps. Can anyone advise me further on this? Thanks...

05-05-2008, 02:25 PM
Measure twice, cut once? :D

Are your joists twisted or cupped? Have you considered joist hangers?

05-06-2008, 11:45 AM
YES, old house. I don't want to create problems. Just thought there might be a handy trick to figure the angles. If both adjacent joists are a little off it is very difficult to measure/fit accurately. My guess is to use one of those adjustable arm things to get the angle for each joist off level, measure the top width than transfer each angle. Time-consuming but should work. Thanks

05-06-2008, 01:07 PM
Use joist hangers, and then cut your blocking to the minimum spacing. You won't have to be so darned picky.

03-01-2010, 04:12 PM
I just checked back on my original postings to this site and 3 years have already passed since my initial demo. The bride and I are tired of, more like fed up with, sharing our master bath. Most prep work done, which turned out to be extensive. Help me move on please...plan to cover walls with 6ml, and seal to tub lip. Question #1--I recall being advised NOT to put the barrier on the ceiling--is that correct? There is a suitable vent light in the middle of the tub/shower alcove ceiling, so moisture removal will be greatly improved. Question #2--if walls are covered with plastic that is sealed to tub edge followed by cement board plus tile--which will get sealed to the tub with silicone--how in the world will moisture in the cement board drain out? More like it's trapped and can only go up, or back out through the tiles. Makes more sense to Redguard, but need advice. Question #3--tub snug in alcove, level along length but slanted slightly into room. Can I just shim the outer part of tub, or must I SLC the tub area? (In)Sanity beckons...

Brian in San Diego
03-01-2010, 04:46 PM

Threads never grow to old to resurrect around here. I merged your new thread with the original so we have the background information. I'll change the title to your new title as soon as I'm finished here.

You are correct in questioning where the water goes and the short answer is "back the way in came in". Many people believe when you caulk that bottom row of tile to the tub surround that you leave a weep hole at both ends of the horizontal run so moisture can escape through there. RedGard is another viable option but considerably more expensive than 6 mil poly. I like the idea of surface applied membranes (whether sheet or liquid) because the water never makes it to the substrate.


03-02-2010, 01:09 PM
Brian--thanks for bringing my old threads back from the dead. My floors are solid, as level as I could get them. But not perfect. My immediate focus is the tub---it slants slightly down from the outside long wall toward the inside of the room, maybe only 1/16th of an inch. If it needs to be perfectly level, can I just shim with a layer or so of roofing felt (or whatever material)? If not, then SLC? Level is good the length of tub...

Brian in San Diego
03-02-2010, 01:33 PM

Is this a new tub you are installing? I am not a tub expert by any stretch but I do read here a lot. Most tubs are set in a bed of mortar and my assumption is that ther can be leveles at that time. If it's existing I think I would be tempted to leave it. You may be able to shim it but I wonder if it's worth the effort. Maybe someone has a different idea.


03-02-2010, 02:33 PM
Brian, The tub is a new Americast Princeton, enamel on steel. Support is by 2 X 4 underside on the long wall and by it's opposite side on the floor, held in by the next layer of underlayment. No bedding required or suggested. I'll await further responses...here's a link to the tub--->http://www.americanstandard-us.com/bathtubs/princeton-recess-bath-with-integral-overflow/

03-02-2010, 03:11 PM
I'll try and help with the tub question... A.S. says not to bed those in mortar but when I set an Americast, I set it in mortar anyway. Why? Makes for a solid, level and permanent install. A.S. has never been able to adequately explain their reasoning behind their "no mortar" suggestion.

I'd remove and reset that tub and make it level. Before removing, check how far out-of-level it is and mark the floor where the tub skirt hits. You can estimate how high the mortar will be by measuring the tub bottom height above the skirt, combined with how far out-of-level it is.

Before mortar, staple down plastic and lath. Any plastic or tar paper will do. Lath available at the box stores or masonry supply yards. Any mortar will do as well. Mix it as indicated on bag and plop it onto the lath. I aim for a few piles directly below the tub floor that can be smooshed down while making the tub level. 2 bags usually does it. A thin layer of plastic over the mortar facilitates tub removal if ever needed. Next day, you can shim the skirt at the floor and attach to the walls.

I don't use foam due to possible reaction with tub plastic, off-gassing and compression. Nothing will give the solid feel of mortar under there. And once heated, the mortar (thermal mass) will hold that heat better than anything else as well. :)

03-05-2010, 03:11 PM
Dana---Thanks so much for the details on leveling the tub. Exactly what I was hoping someone could provide. Your suggestions made my day! Very much appreciated

03-05-2010, 04:02 PM

Just checked your link and installation instructs. Didn't see the prohibition on mortar???? Maybe I missed it or they changed it???

Doesn't matter to me anyhow, just curious..............................

03-10-2010, 11:45 AM
Dana---Found this sticker on the tub "DO NOT USE SUPPORT MATERIAL (e.g. CONCRETE, MORTAR, STRUCTOLITE) UNDER THE TUB. USE OF SUPPORT MATERIAL WILL VOID WARRANTY". My concern is not the warranty but rather getting the tub properly level. After going through 3 different gents at Lowes, the fourth suggested structolite, claiming it's a much simpler process. I don't have a clue, but like the 'plopped blobs of mortar method' better. Do you think one 60 pound bag will be enough? I am still fiddling with the tub, want to see if fine-tuning the stringer can help level.

03-10-2010, 04:27 PM
Thanks Andy, I thought I'd seen it somewhere. :)

I'd get 2 bags, mix 1 and see if it looks like enough. Mix up the second one if needed, or take it back if not.

03-13-2010, 06:14 AM
Lastly, I assume focus area is just under tub basin, maybe like 2' x 4'. Blobs of mortar mix, no need to cover/mesh/mortar the entire alcove floor area under the tub(correct me if I'm wrong). It's time to gitterdun.

05-11-2010, 08:25 AM
MY previous post now 2 months back and no progress. My hands are tied but the good news is that I have been gifted the completion of this project. I have interviewed several candidates but none have really fit the bill. So, if there is anyone interested, please contact me. Project entails minor plumbing and framing; tub install; prep and installation of marble tile in tub surround and floor. Project dates Tuesday 6/15 to Saturday 6/19. I live in West Islip, NY. Will be able to assist if needed. Please contact me asap if interested. Thanks

05-11-2010, 08:33 AM
I took the liberty of copying and editing your last post into a new thread in the Pro's Hangout ("HELP WANTED! long island, ny,") where it may catch someone's attention. If you would like to elaborate on what I've done, please feel free.

05-11-2010, 08:52 AM
Thanks Bob, excellent idea. I've gained enough from this forum to ably interview prospective job candidates. It is amazing to me how divergent the opinions are about tiling, especially when it comes to waterproofing. Hoping for a quick response...