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Jake12 12-12-2021 03:07 PM

Bath Remodel
Back again working on my main bath. New project.
Wanted to check my sub floor with you.
I’m going to put in Ditra Heat with porcelain tile
I’m replacing a garden jetted tub with a 55” freestanding tub which will be in the same basic place.

I have 10” joists Douglas Fir.
10 ft span
16” centers
It’s covered with 19/32 sturd-I-floor
APA rated oxboard

It had tile on it and no issues but thought I’d double check. Deflecto shows
good but not sure on the sub floor?

Appreciate your input.


cx 12-12-2021 06:26 PM

Welcome back, Scott. :)

You have nominal 5/8ths" subflooring plus this Oxboard? The Oxboard is their ThermoPLY sheathing, or something else?

Jake12 12-12-2021 06:58 PM

2 Attachment(s)
I’ll try to upload picture of label on the floor

Jake12 12-12-2021 07:05 PM

All I have is the one layer

ss3964spd 12-13-2021 11:14 AM

Your 10' long, 10" tall DF joists are plenty stout, Jake, and Schluter says your 5/8 OSB is stiff enough given the 16" OC joist spacing, as long as the OSB is tongue and groove.

Still, many folks feel that 5/8" is a bit thin, and would opt to install a 2nd layer of 1/2" thick actual plywood. If you can afford the height gain, that's what I'd do (and did in my current bathroom remodel job).

Jake12 12-13-2021 01:20 PM

Thanks Dan

Found some info on the mfgs website about the floor. Looks like they do recommend additional subfloor for tile. Designed for carpet.

My challenge will be toilet flange is currently only 5/8” above the existing sturdi floor. Will I need to raise that? The bath exits to carpet which was level with old tile but assume I can deal with that?

So assume the recommendation is to add the 1/2”?

There’s also a cut out for old tub drain and I need to open that up more to move to new drain so thinking that is another reason to add the 1/2”.

Any idea if Homers carries an adequate grade of plywood?

What size screws do you recommend?

Thanks for the help

ss3964spd 12-13-2021 01:54 PM

Ideally, Jake, you'd raise the flange so that it ends up resting on the finished tile floor. Not always possible in a remodel. There are various options, like a thicker wax ring or flange extenders. There might also be enough wiggle room with the waste line, could try to un-screw it from the floor and see if you can pull it up a little.

The new tile floor to carpet transition can handled by a transition strip, typically wood.

Yeah, if the Oxboard manufacturer actually recommends another layer of ply for a tiled floor seems like you ought to heed their suggestion. 1/2" ply (not OSB) is recommended, with no face grade lower than "C", and with an exposure 1/EXP 1 rating, installed with the long edge perpendicular to the joists. Depot will likely have it, mine does. Screws - I'd go with 1 5/8" construction screws. If the existing OSB is nailed down you might also consider screwing it down before installing the 2nd layer.

Jake12 12-13-2021 02:57 PM

Thanks Dan. I’ll investigate the toilet flange further.

Otherwise sounds like a good plan.

Jake12 12-15-2021 11:24 AM

Looking for input on a knee wall between shower and freestanding tub. As I research it finding there may be a need for more structural support than I had envisioned.
I saw an option with all thread connected down to joists or connecting 2 x down to joist
Then ran across Kerdi Board which seems interesting and from what I saw I could put 2 / 2” PCs together and use thin set or fix to attach to wall and floor but is that secure enough?
The joists run parallel to the wall
I’ll post a picture of the area
I’m thinking it will be approx 32” wide and 30” tall. Is that a reasonable height?
Appreciate any guidance to a good solution.

Thank you


Jake12 12-15-2021 11:26 AM

1 Attachment(s)
Tape on either side is joist location

cx 12-15-2021 11:32 AM

The pony wall is to serve some practical purpose, or is it just a design feature?

Jake12 12-15-2021 12:55 PM

Design. Some separation from tub and so shower is not all glass. Half glass on wall.


ss3964spd 12-15-2021 01:46 PM

Jake, when I built my half wall I was able to screw the sole plate into the floor joist. Indeed, all of the framing for the half wall (which also houses the niche for the shower) is screwed together. It still moved when pushing on the outside corner.

Covering it with foam board and sheet membrane for the seams, top, and end helped a bit, as did the shower side corner bench, but what eliminated the movement was installing the stone top and end pieces.

Jake12 12-15-2021 02:15 PM

As you see my joist is just out of reach and runs parallel. So i suppose I can open floor put in bracing and tie 2 x to that?
I’m not planning any other piece that would give some support like your shelf. I would like that and had considered a bench but not much room.
Does that sound like best option?
Is tile stiffing it up enough structurally as yours turned out?

How about the Kerdi board option any opinions on that?


ss3964spd 12-15-2021 02:48 PM

2 Attachment(s)
Your username, "Jake", is really throwing me off, Scott. ;)

What I was trying to suggest was even if you could screw it into a joist it is still going to move. Though I cannot confirm, I'm pretty certain the Kerdi board option is also going to move if you push/pull on that outside corner.

The "floating" corner bench (Better Bench) I have really doesn't take up much space. Mine is situated in the corner of the half wall and the 39" ish end wall where the fixed shower head is. The bench never gets in the way. To verify, you could cut a piece of cardboard into a triangle roughly the size of the bench and tape it in place.

Between the bench, the membrane, tile on the shower side, and stone top and end pieces that wall doesn't budge.

Jake12 12-15-2021 03:42 PM

Is the counter supporting too?
I’ll look into a small shelf. That would seem to give it some support.

Nice work on the shower.

Jake or Scott is fine. :)

ss3964spd 12-15-2021 04:18 PM

Nope, the vanity top is not supporting the half wall.

Jake12 01-13-2022 02:26 PM

Moving slow but sure.
Installing the Ditra Heat and anticipating correct thin set to lay tile on top of the Ditra Heat. 12 x 24 porcelain.
I’ve worked with Versabond LFT. Is that appropriate in this situation?
I believe I confirmed it on other threads but also see comments that Ditra and Ditra Heat are different.
Understand the warranty is out but have used Versabond on my other Kerdi projects with no issues. Just first time with Ditra Heat.


ss3964spd 01-13-2022 03:14 PM

Regular Versabond, or VB LFT will do the trick, Scott, I used regular VB to install 12X24's on toppa Ditra Heat. Worked great. I did pre-fill my Ditra Heat mat.

Jake12 01-13-2022 03:26 PM


Can you clarify “prefill”? Is that like burning in some thinset to fill voids and then troweling over that all at same time or filling it with a smooth layer letting dry and then putting troweled layer on?
Thinking it’s the first but made me think a bit.

ss3964spd 01-13-2022 03:53 PM

2 Attachment(s)
Schluter says you can fill the Ditra and lay tile all at once.

I say I was confident that I wasn't competent enough to do so, at least not without making a giant mess. So I opted to install the cable then pre-fill the Ditra completely. I let the VB cure for a number of days.

Due to the thickness of the VB I found it shrank a bit after curing so, because I'm a little ODC-ish, I skimmed on another coat. In hind sight the second coat was likely unnecessary but, well, OCD. A few days after the second coat I started setting tile. You might be able to make out the difference between the 1st and second coats in the photo below.

cx 01-13-2022 04:28 PM

Heeey! That's not no steenkin' Ditra. :D

Jake12 01-13-2022 05:42 PM

What do you suggest?


cx 01-13-2022 06:31 PM

Pay no attention to me, Scott. I was just picking on Dan a bit. His advice is always sound, which is why the site owners hired him and pay him the big bucks, eh? :D

Jake12 01-13-2022 07:11 PM

So the bonding strength is the same if I do the skim coat to fill the voids and let dry then set tile?
Does seem to make the process more manageable. So I can focus on keeping wires in tact and fill the voids.
I’m leaning towards the LFT so do I have to use same thin set for both steps or can I use regular Versabond for first coat then LFT for tile?

Thanks guys for all the help and input.

cx 01-13-2022 08:04 PM

Schluter prefers that the voids be filled while the tiles are being set, Scott, but they also condone pre-filling the voids and setting the tiles as two separate operations.

They even "allow" you to use modified thinset mortar for filling the voids if that's then allowed to cure before setting the tiles, where they require an unmodified mortar. In reality, it needn't be all that complicated and you could use either of the mortars you mentioned for either of the operations, you'd just not benefit from Schluter's warranty, which you'd not benefit from in any case.

My opinion; worth price charged.

Jake12 01-13-2022 08:08 PM

Ok. Thanks Dan & CX. I have a day or two to contemplate and firm up the plan. Your input is a big help.


ss3964spd 01-14-2022 08:58 AM

Remember, Scott, that the thinset mortar doesn't actually "bond" to the Ditra (Heat), it is mechanically held in place by the way the columns and channels are formed.

The VB LFT you contemplate using has, I believe, a larger aggregate than does regular VB, and that larger aggregate is what helps the LFT mortar prevent LFT tiles from sinking into the mortar under their own weight. The thicker the mortar layer the more prone the tiles will be to sinking. The larger aggregate might also help reduce shrinkage.

I used a 3/8" slant notch trowel for setting all my 12x24 tiles, as well as a lippage control system, so never had that sinking feeling using regular VB.

In the end prefilling the Ditra (twice!) was an anxiety reduction method for this relatively inexperienced tile setter. Didn't have to worry about ensuring the voids were completely filled, or about combing wet mortar out of the voids, or about nicking the cable, all while simultaneously setting tile and ensuing good coverage. Only down side were the extra hours involved.

Don't forget to test your heat cable before, during, and after.

Jake12 02-10-2022 04:58 PM

1 Attachment(s)
Got an issue. My drain bottomed out when I was putting it in place. Not sure why but it would not go any lower. I thought I had the 11/4” space. But it was not going any deeper. At the time I thought it was close enough but now that I’ve grouted it’s leaving a puddle.
Any options short of tearing out? Had plenty of slope just got the tiles by drain too low I guess.
Was so concerned with all comments about difficulty of laying pennies and counted on ease of the adjustable Kerdi drain. Should have backed up then but that was then. Very frustrating.

ss3964spd 02-11-2022 08:15 AM

Even if you could lower the drain you'd have to remove some of the area around it to do so. I don't see any other options.


Jake12 02-11-2022 09:17 AM

Thanks Dan
So start taking tiles out? Looks like I’ll need to go 6” or so around drain to establish a new slope.
They’ve been in for about a month. Grouted a week ago.
Any recommendations on how best to do that? Should I get the grout out first or just try to pop the small ones by drain and see how it goes? Will I tear into Kerdi or should they separate above the Kerdi and then I can carefully clean down to Kerdi? I’m sure it will all vary but any tips on what I’m getting into is greatly appreciated. Tools, techniques, etc.
obviously killing me that I let this happen.
Everything else is finished and happy how it turned out. Can’t believe I messed this up.

Thank you

ss3964spd 02-11-2022 10:57 AM

I dunno, Scott, it depends on how much slope you have. If you remove the pennys, build up the area below, and reinstall them with less resulting slope you might just push the puddle out farther from the drain.

Regardless, the Kerdi does complicate things. If removing the pennys and the grout pulls the fleece off the Kerdi there won't be any left for the new mortar to bond to. Or, if the pennys and grout are really well bonded to the Kerdi, you run the risk of the Kerdi getting lifted off what it is adhered to below.

You won't know how it's going to go until you try, but it could be a whole can full of worms.

I'd almost consider cutting some slots into the edges of the stainless drain body. I'd definitely consider a squeegee.

Jake12 02-11-2022 11:16 AM


OK that’s what I’m thinking.
Notching the edge seems to be a good step. Any idea how tough that material is to cut? What tool would you recommend? Thinking a notch on each side.

Definitely squeegee for glass and floor. But I think I need to try something to improve it.

Thanks for the guidance.


ss3964spd 02-11-2022 12:08 PM

Cutting slots into the lip around the grate will only work if the lip is solid, and I have no idea if it is.

If it is, it won't be terribly hard to cut. First tool that comes to mind is a Dremel with a metal cutting disk. If I were going to do it I would measure carefully and cut a slot in the center of each of the 4 sides. I'd probably follow that up with a small, triangular file to create a V shaped opening. Be certain to remove any burrs. Might need to create corresponding slots in the bottom edge of the grate. Done right it might even look like they're supposed to be there.

Jake12 02-11-2022 01:14 PM

1 Attachment(s)
Fairly soft material. I used a multi tool. Worked pretty well.
I cut the 4 and a big help
However it is relatively thin. You can see looks like I cut through on the first one. What problem did I create now? Can a caulk that? Where will that water go?

Otherwise I think I’m getting close. Like the filing suggestion too.


ss3964spd 02-11-2022 03:33 PM

Yeah, I see the hole, confirms that it isn't solid.

I don't think it's a problem though. Any water that gets in there is just going to hit the top of the flange and go down the drain.

Jake12 02-11-2022 04:42 PM

Thanks again Dan. That worked out better than expected. Drains a little slow but clears the surface water after not too long. I left it alone last night and the water never completely cleared. I was obviously very stressed. We’ll plan to wipe down but good it’s resolved for future.
On the Ditra Heat the pre filling was sort of a waste. I ended up walking over it many times to get access and I lay tile like a turtle. Anyway many of the “buttons” popped out and made a pretty good mess. A few ended up in my thinset but fortunately I think I caught all of them or my troweling was thick enough I didn’t have one hang up under a tile. It did stay intact over the cable so probably worth having it there to protect cables. Just thought I’d add for others benefit.
The cables tested out good. Have an electrician coming out to put a new breaker in next week and will hopefully all turn on properly.
Don’t know what I would do without the support and confidence you guys all provide to us. Can’t thank you, CX and the rest for the help.
I’ll post a pic.

Jake12 02-11-2022 04:44 PM

1 Attachment(s)
Didn’t go with the half wall. Glass is being installed next week.

ss3964spd 02-11-2022 05:13 PM

Huh, I didn't have that issue after pre-filling my Ditra Heat. Just curious, did you use a modified or unmodified to pre-fill?

Don't let your sparky install a GFCI breaker, the floor controller has one built in. I'll be curious if your floor makes a very brief audible crackling noise the very first time it is energized. Mine did - most unsettling. But it's been toasty toes for 3 seasons now.

Jake12 02-11-2022 05:56 PM

I can’t guess how much I walked over it. I think I got sidetracked on some other things and probably 100 in and outs over a few days. Where I was able to stay off it it held pretty well.
Appreciate the heads up on the Ditra Heat.

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