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-   -   Early 50s bathroom renovation looking for feedback (http://www.johnbridge.com/vbulletin/showthread.php?t=124235)

kickstart 12-06-2017 05:14 PM

Early 50s bathroom renovation looking for feedback
Hi there, DIYre new to the forum and never done a bathroom renovation or tiling job before :)

Im hoping to get some feedback on my bathroom remodeling plans, especially with the floor tile installation.

Im planning on gutting and re-doing my early 1950s second floor dormer bathroom (full bath). Im planning on replacing all fixtures, wall tile and floor tile (basically gutting to the studs and redoing everything). I realize this will be a big challenge. On the more optimistic side, Ive been doing a lot of research and even got myself a copy of the 2017 TCNA Handbook.
Regarding the floor here are my constraints (challenges) Im working with for this remodel:
  • Wife already picked out a 7/8 mosaic hex tile
  • We want electric heating under tile
  • This dormer bathroom is only a little over 7 high at the highest point, sloping down to a little over 6 at the lowest, so Id rather not lose any more headroom than I need to.
  • In addition to the low ceiling height, the hallway outside the bathroom (and the rest of the house) has 5/16 face nailed hardwood flooring, and theres already approximately a 1 step/threshold to the existing bathroom tile floor so, again, Id rather not build up the new tile floor height much more than it already is.

Some positives:
  • Its a pretty small bathroom (about 5x8) including the tube area (so only about 5x5.5 floor tile area)
  • The original tile floor is actually in really good condition. Only one small crack behind the toilet and is pretty level with just a slight drop (about 1/8) towards the tub. So Im thinking my joist support is probably adequate for what Im putting down.
  • The upstairs appears to have a 3/4 plywood subfloor. (The first floor has 1x4? T&G solid boards)

Heres my current plan for the new floor:

Using TCNA RH135 for interior floors with radiant heat over wood as a guideline, as follows:
  1. Rip up the old plywood if its too water damaged and replace with 23/32 EGP, glued and screwed to the joists
  2. Apply modified thinset and then 1/4 cement backer board screwed to the plywood
  3. Tape and seal (thinset) seems in backer board, let dry
  4. Prime backer board with SLC primer
  5. Attach Suntouch TapeMat to backer board with staples to secure the mesh and hot glue to secure the heating wire.
  6. Run 1/4 foam insulation band around perimeter, and seal all gaps with latex caulk
  7. Apply SLC (LevelQuick RS, or ES?) to a thickness of 3/8 to 1/2 to just cover over the heatmat level/feather, let dry
  8. Apply mosaic tile with modified thinset

Thoughts on the above? Any glaring admissions?

A few notes:
  • I using RH135 instead of RH130 because I want the Res 2 wet rating of course Im using SCL instead of Mortar but believe SCL is technically a modified mortar itself
  • Im using 1/4 backer board to save some height, but using the 23/32 EGP (instead of 19/32 allowed per spec) because Id like a little more rigidity. Does this make sense?
  • This should get me to around the same height as the existing tile floor (I think), at about 1-1/14 above the hallway floor maintaining the same threshold step-up I currently have
  • I would prefer to use Ditra Heat, but I dont want to chance the installation with the smaller mosaic tile
  • Im using SLC because it seems to be a lot less of a hassle and a better finish than doing two coats of thinset, and not that much more of a cost for a small bathroom
  • Ive read the library thread on SLC, and I see that one suggestion was to spray the primary over the heatmat, but I called Suntouch and they suggested not to prime the heatmat.

Thanks in advance for your help, suggestions, and feedback!

rmckee84 12-06-2017 05:26 PM

Seems like you have a good grasp on things. One thing I can say is LevelQuik isnt rated for over CBU. Mapei has one just called self leveler I believe and it is good for use over primed CBU.

kickstart 12-07-2017 06:44 AM

Thanks for the tip Ryan!...

I just assumed Levelquick was good over backerboard. I'll look into the Mapei SLC.

rmckee84 12-07-2017 04:04 PM

I recently came into a project that was already prepped and needed to use slc to cover heating mat so I contacted Custom and they told me I couldn't use any of their slc products over cbu.

kickstart 12-07-2017 06:24 PM

The realization that this tiling stuff is a lot more involved than I originally thought has started to hit me :)

I chatted with Custom (online support). They said Levelquik can be used over CBU (specifically, they said Wonderboard), but.. that you need to prime and use lath (similar to the requirement for use over wood).

Per your suggestion, I found that Mapei has a SLC that specifically states you can use it on CBU, and use it to encapsulate electric heating wire - Novaplan Easy.

I also called Mapei. I forgot the guys name I talked to (sorry), but he seemed pretty knowledgeable. He said to prime with Primer T and there's no need to use lath, at least for an area as small as a bathroom. BUT... here's the kicker... when I asked which of the many SLC's they sell to use (expecting him to reply with "Novaplan Easy"), he said any of them will work fine over CBU. :shrug: Anyway, I think I'll go with Novaplan Easy. Now to find a place that sells it.

The Mapei tech support guy had some good suggestions:
He said he'd prefer to use heat wire instead of the heatmat as that would give the SLC more contact area with the CBU. He would also like to have the primer applied after the heatwire was fastened down, due to possibly contaminating the primer coat by walking on it when installing the heat wire. I think I'll double check with the mat manufacturer and see if it's OK to prime the heat wire.

So... there isn't a good consensus on the finer details here... as in what SLC's are OK to use over CBU, or which ones are the best in this application... or the best way to embed heating wire/mats.

It's funny, I ask the heating mat company about how to go about embedding the mat in SLC and they say "what do do the instructions of the self leveler you're using say, you need to follow their instructions"... and I ask Mapei support the same question, and they say "you need to follow the instructions from the heating mat manufacturer" :)

kickstart 12-08-2017 12:17 PM

Thinking about my subfloor prep some more... I'm wondering if the 1/4" of CBU is redundant if I'm using SLC.

I see TCNA has a spec - RH140 which is just 1/2" of SLC on top of 3/4" ply, with the heat wire encapsulated in the SLC. It's only a Res1 rating... but maybe I'm better off putting a membrane on top of the SLC anyway, especially considering the floor can get pretty wet next to the tub (at least in our house).

rmckee84 12-08-2017 03:10 PM

CBU adds no strength to a floor so I would say there is no real advantage to adding it.

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