Question on simple powder room reno

[psumichael]

Hi all,

I'm back after many years!

Renovating a small powder room. Removed majority of old tiles. Turns out they were laid directly on top of plywood. Looks like they were on a 1/2" layer of plywood which is on top of the subfloor (I believe it's 3/4" plywood).

I bought some Ditra; it should arrive within a few days.

My question:
Given the 1/2" layer of plywood on top of the subfloor has a fair bit of mortar on it and is also "frayed" in certain areas, should I remove the 1/2" layer and simply put Ditra on top of the subfloor? This would have added benefit of allowing new tiles to go under the existing baseboard without having to remove that baseboard?

Thanks,
psumichael

[cx]

Welcome back, Michael.

That would depend upon your joist structure and what your first layer of subflooring really is.

[John Bridge]

Hi Michael,

I would replace the half-inch layer. Also, remove and re-install the quarter-round molding at the bottom of the base.

[Snets]

Honestly, I would never re-tile without removing baseboard. Trying to tuck tile under baseboard is far more time consuming than installing and painting new baseboard....and using 1/4-round to hide gaps is frankly unacceptable in my book. Never done it, never will. (Sorry, John Bridge, I mostly only work for myself so being a perfectionist doesn't cost me money)

[ss3964spd]

Looks like a common 5 1/4" colonial baseboard, Michael, but in the 2nd photo it appears the 1/4 round is actually floating above the tile. Maybe it's just my eyes. I also can't tell if the base was installed first, then the 1/2" ply, or if the ply is under the base.

Regardless, if you elect to remove (then replace) the 1/2" ply you may find that you can't get it out without removing the base, or at least that 1/4 round.

Cart/horse though. Back to cx's comment.

[psumichael]

Thanks, all, for the feedback!

I removed and scrapped the 1/2" plywood that was covered in old thinset. The subfloor is 3/4" plywood (joists 16" O. C.). Given that that is a perfectly acceptable subfloor for Ditra installation, and that tiles I'll be laying are thick (14mm, slightly more than 1/2"), I opted to move forward without adding back a new layer of 1/2" plywood.

I put some more screws into the plywood to be certain it was completely locked down to the joists. Mixed up some grey Versabond. While I let it slake, I wiped down the plywood subfloor with a wet sponge.

Then I applied the thinset using Ditra 11/64" x 11/64" trowel, first installing small piece of Ditra and then larger piece. I pressed it into place using a float.

The Ditra seemed to go down relatively well. A couple of hours after installation though I noticed that there is a splotchiness through the transparency of the Ditra, almost as if some of the thinset cured differently than the rest or that it is thicker in some spots than others. With some lighting it's hard to even see but it's definitely visible with some lighting conditions.

This morning, about 16 hours after installation of the Ditra, it looks the same. If I really try to find waviness with bare hand running across the surface there are some spots where I may feel some. It feels solid when I walk on it though - no indication of movement or lack of bonding.

Is this anything to really worry about? I can't imagine trying to tear up the Ditra and remove the thinset - that would be absolutely brutal.

Thanks!

[ss3964spd]

I think the splotchiness is as you suspect, Michael, a bit more mortar in those spots. As long as you can't feel any movement in the lighter looking areas it should be fine.

[psumichael]

Thanks, Dan! That's the answer I was hoping for.

On to a never-ending debate...
I'll be installing either of these porcelain tiles over the Ditra:
https://www.homedepot.com/p/MSI-Cign...G8X8/306155337
or
https://www.homedepot.com/p/MSI-Aman...A8X8/303116971

What's the latest advice on whether to use modified or unmodified thinset with porcelain tiles of this size over Ditra? Does it really come down to how long you'll wait until you grout, with unmodified setting much faster and thus more appropriate if grouting quickly after installing the tile?

Thanks!

[cx]

Originally Posted by Michael

...with unmodified setting much faster and thus more appropriate if grouting quickly after installing the tile?

The curing time is not Schluter"s concern, Michael, it's the drying time of some types of polymers in some types of modified mortars.

With those small tiles, i'd not be concerned at all. i don't thnk grouting after the standard 24Hr. cure time should be problematic. See my warranty information below.

I'm a bit curious as to just what they are. Homer says they're both encaustic and porcelain. Not sure how that computes.

My opinion; worth price charged.

[psumichael]

Thank you, Sir!

I didn't really catch the term "encaustic" until you highlighted it. Looks like many manufacturers are deeming their tiles encaustic and porcelain (https://www.lowes.com/pl/Encaustic--...ent=1145863273). Perhaps manufacturers are using a more liberal definition of the term "encaustic."

[jeffnc]

I don't really agree with snets. Removing and reinstalling baseboard can be quite time consuming, especially when you factor in the unknowns of damaged walls and damaged baseboards, both of which occur fairly often. You don't even know what that baseboard is made of - if it's MDF, then it's even worse. Obviously the use of shoe molding/quarter round is a subjective thing, and I like the use of it, but even if I had to slide tile under baseboard (which I would rarely do) I would still prefer that.

Onto the Ditra installation. You're probably fine. It sounds like you did everything right and what you're probably seeing is how the thinset soaked through the fabric more in some places than others. If you made a " mistake" at all it could have been the thinset wasn't mixed fluid enough, but even that shouldn't be an issue as long as it didn't have a chance to skin over.

I would simply use a good unmodified thinset. With smaller tiles like 8"-, you could also use modified but I don't see much point to it. The whole point of Ditra is to avoid things like cracked tiles in case there's any movement, so one of the big benefits of modified thinset is lost anyway. With unmodified thinset, you are probably better off grouting sooner rather than later.

[psumichael]

I've done my initial tile layout and am ready to start cutting tiles. One quick check first... I've lined up the center of a main feature of the pattern with the centerline of the toilet, which is also the centerline of the walls on either side of the toilet. This means the pattern is not centered in the doorway. Is this the best, or at least reasonable, layout approach?

[jeffnc]

Centering on the toilet line makes sense. I can see the left side will be a bit less than a full tile, will the right side as well?

[psumichael]

Thanks, Jeff. Yes, width of cut tiles along right side wall will be roughly 6 1/2" (uncut tiles are 8" square).

[PhilWA]

Purely subjective, but I'd consider laying out the tile to prioritize whole sections of the 4-leaf clover pattern where possible. That would mean shifting the pattern down and to the right by one tile. But lay it out however you like in the end.