Any advice on "thin" porcelain tile?

[chriswand]

I'm hoping that some of y'all have experience to share regarding so-called "thin" porcelain tiles.

The situation is that we're looking to tile an area in our basement in front of a wet bar. The tile we like (from an aesthetic standpoint) is a 8"x48" thin porcelain tile (tile thickness is 6mm, so it's about half as thick as the porcelain tile I'm used to); it's billed as being able to be laid over existing tile without tear-out of old tile and base, but in our case this will be a new install.

At 48" long and thin, the tile has some decent flex to it, and I don't want to end up with any post-install issues like cracked tiles. (In case anyone is wondering, it's the Maximo Wynwood Gray tile from Floor & Decor; it appears to be exclusive to F&D and I can't find a lot of info on it). I don't know if the flex in the tile works to our advantage or not.

The underlayment would be Laticrete Strata Mat, the subfloor is 3/4" plywood over 11-7/8" high TJI 25 DF Trus Joists spaced 16" OC spanning a distance of just under 16'. According to Weyerhouser's span tables, that joist can span 19'3" at 16" OC and yield an L/480 deflection (a span of 21'4" at 16" OC would yield L/360 deflection, though our application doesn't have a direct applied ceiling on the underside of the joists which would reduce the spans a bit). (And, yep, in case you're wondering, the basement floor is a structural wood floor over a crawlspace thanks to expansive soils.)

If it makes a difference, the area to be tiled is about 21' long x 5' wide, where the 21' dimension is runs perpendicular to the joists and one long side of the tiled area will abut the exterior wall supported by foundation (so the tiled section isn't mid-span on the joists). The long side of the tiles would also be running perpendicular to the joists. In the attached photo, the area to be tiled is the light grey area under the cabinetry; the floor joists run top to bottom and the tile would run left to right.

If the tile was a standard thickness porcelain tile, I wouldn't anticipate any issues, but given it's both thinner than normal and a fairly long tile, I'm wondering what y'all with real-world experience would say. Thanks in advance!

Chris

[jadnashua]

I'd read that 5mm and thinner tile tends to have issues, so in that regard, it should be okay.

When dealing with a tile that long, the flatness requirements of the surface become much more stringent...your floor probably is NOT flat enough without help. So, the first thing you need to do is get a long straightedge (8-10' is recommended), and check for flatness (level is nice, but not required).

Then, when installing, you need to be really careful about proper setting of the tile...I highly recommend you look for a slant-notched trowel which ends up with a much flatter, gauged surface than a V, square, U, or whatever shaped notch. You want nearly perfect coverage with the tile, which is one reason why a long tile needs a flat surface, and because it is large, pressing or moving the tile to flatten the peaks of the trowel marks is REALLY hard on a large tile, so a slannt-notched one where it's nearly flat already makes a big difference.

You said basement, but plywood? If part of it is on a slab, see if there are any slab surface cracks, and how wide, and if the edges are the same elevation. That may dictate some other avenue. Displaced height edges mean the slab should NOT be tiled.

[cx]

I've added a link to what I think is your tile product, Chris. If it's not correct, please change it.

I don't see any indication that this tile meets the requirements of ANSI A137.1. That doesn't mean there's anything particularly wrong with it, just means we have no way of knowing much about it.

In their Questions section, they (F&D?) say the tiles are rectified. If they're actually cut from Gauged Porcelain Tile Panels, I can see them being reasonably flat. Otherwise, at barely a quarter-inch thick (depends upon where you read in that link), I'd expect a good deal of warpage. Tough to say without having some in hand.

I wouldn't worry much about your joist structure, presuming it was installed correctly with the appropriate bracing across the bottom of the joists.

The subflooring, on the other hand, would worry me some. Yes, it's technically a ceramic tile, and the single layer of nominal 3/4" subfloor, if properly installed, meets the minimum requirements, but those tile are not gonna have a lot of strength. Again, without their meeting any testing standard, we don't really know.

Jim's point about flatness is certainly well taken, too. The minimum requirement for flatness of the substrate for tile with any dimension longer than 15 inches is no deviation from intended plane of more than 1/8th" in ten feet, nor 1/16th" in two feet. Very uncommon for a wood-framed floor to meet that standard without help.

My opinion; worth price charged.

[chriswand]

Thanks for the reply Jim. I hear you on the flatness and am definitely planning on verifying that. I've not used slant notch trowels, but can always use another trowel in my collection ;-)

Regarding the subfloor, the entire subfloor is plywood even though it's in the basement. Due to the expansive soils, the builder didn't pour a basement slab (which would have a tendency to heave with the soil, causing any interior basement walls to also lift up), so the basement subfloor is framed just like a traditional floor with joists and plywood on top, with a crawlspace below.

[jadnashua]

Because the tile appears to be somewhat flexible, you might find a floor leveling clip may be helpful.

[chriswand]

Thanks CX! That is indeed the correct tile. The tile is actually rectified, and pretty darn flat--when I sight down the edge of it while holding it in my hands, there is a very slight bow (it bows up in the middle towards the finished side of the tile), but when I put it on our quartz countertops, the weight of the tile causes it to completely flatten out.

I've never used a tile that flexes like this one--it's not spaghetti floppy, but if I put a 1/4" thick piece of plywood under each end, a moderate amount of pressure from my hand in the middle of the plank can cause it to bow down to touch the countertop, and it doesn't feel like it is flexing so far that it would crack. Is this going to be a nightmare to work with due to the flex? I'll be using a tile levelling system (Raimondi RLS) since the rectified edges aren't going to be very forgiving of lippage.

[cx]

Originally Posted by Chris

Is this going to be a nightmare to work with due to the flex?

Dunno what your nightmares are like, Chris, but I'm betting those tiles are gonna get your full attention.

I've never handled a tile that flexible, but the lippage control tools might be very helpful. Maybe more than would usually be desired, 'specially if you're planning to set the tiles with varying offsets. I'll be curious to hear how it goes.

My opinion; worth price charged.