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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.

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