Sunken shower pan + raising bathroom floor

[MolsonB]

We are redoing our master bathroom and the chief finally found a tile she liked. Comes in 12x24 or 18x36. The only problem (?maybe?) is that they don't stock the matt rectified version and would take 14 weeks from Italy to come in. About $8 Canadian sqft.

The bathroom will have a curbless/doorless heated shower, so the same tile will be used for the whole 120sqft floor. We want a seamless look, which is why I read that rectified is the only way to go.

I've done a few Travertine lays and liked the 1/16 grout lines. Never have I done 18x36, so I don't know how important rectified is with large format tiles. Worth the wait ?

[speed51133]

are you setting the tiles? has the person installing them installed tiles this large before?

it takes special equipment and more than one person. I mean I would not trust any person to set it.

[MolsonB]

Hi Mike,

We'll be installing it ourselves. What kind of special equipment would be needed? Other then an extra set of hands. Biggest I've personally done is 24x24's.

I'm not opposed to dropping down to 12x24, but the company doesn't have them in rectified stock either.

[ss3964spd]

Just a DIY'er, Matt, and just recently finished my curbless/doorless bath over haul using rectified 12X24 wall and floor tile (except for the shower floor - 2"X2").

I, too, prefer a narrow grout joint. I think you'll have a heck of a time using a 1/16" joint with those big unrectified tiles. It will even be a bit of a challenge if they are rectified. About the only way you'll be able to tell is carefully measure a bunch of them for L & W, and from different boxes.

[MolsonB]

What grout line did you end up going with?

I guess that's my real question. Why would people get large tile that is not rectified?

[speed51133]

I was kind of thinking along the lines of porcelain slabs/panels. But...

One thing is suction cups to place them. I would get some quality glass/slab handling suction cups.

You should also use Euro slanted trowels to help ensure you achieve full thin-set coverage.

You also need a good way to move them from point A to B without damage. Do you know the thickness and weight of each?

Another is just room. You will want to back butter them and having something to rest them on will help.

[ss3964spd]

I used 1/16th for the walls, and 1/8th (because I had to) on the main floor.

[jadnashua]

Industry standard on grout width minimum is 3x the variation from the largest to the smallest. To use a 1/16" grout line, the tiles would need to be identical to within 1/48" of each other all along the edges.

On a large tile, you end up putting thinset on both the surface and the back of the tile. I'll second the use of a slant-notched trowel. The suction once in place means you'll almost never get the opportunity to move it back and forth to spread the notched material out to achieve full coverage. You have a chance with a slant-notched trowel as the surface will be nearly flat once you've spread the thinset and the notches fall over to fill in the gaps. The tile is fairly rigid, so the amount of pressure you can applied is almost nil on a large tile. Say you could put all of 200# on the tile, an 18x36" tile, that would only amount to about 3.24psi...you'll not get the peaks of a notched v or square notched mortar to fill in the gaps without lots of movement. YOu really can't do that with a large format tile.

[MolsonB]

https://www.casaroma.ca/en/flooring/terra

The 12"x24" is 10mm thick at 8lbs while the 18"x36" is 11mm thick at 24lbs. No issue's there with weight. Have lots of room for staging them.

I never heard of the Euro slanted trowels, I'll look into that if a go with the 18'x36' tile.

When I back buttered the last job, I added some notches going the other direction then the floor. Helped give me a little more play with the cuppage in the tile. Using the T-Lock leveling systems have really helped the average DIY'er.

I still leaning towards the 18"x36", but need to find a different tile that is stocked in rectified.

[jadnashua]

If you've got notches on the tile and floor at 90-degree angles to each other, you can end up trapping air underneath. I haven't taken a class on large format tile in a long time, so don't know the latest suggestions, but I'd want to get the latest techniques to ensure you have the best chance for success.

https://www.contractorsdirect.com/br...SAAEgJpdvD_BwE

[cramby]

My experience with ceramic and porcelain large format tile would recommend that you try to get the rectified tiles. Cut stone tiles are more reliably rectified but the baked ones have some variations that can be challenging to work with, especially with small grout lines. Having said that, if you are willing to live with some grout line variations and mild lippage in spots then keep the 1/16 grout space but I’d encourage you to wait for the rectified tiles.


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[cx]

Matt, the industry standard Caliber Range (variation from average facial dimension) allowance for Calibrated (not rectified) tiles exceeds your proposed 1/16th" grout joint width by more than twice if you have a tile at each the smallest allowable and the largest available.

The allowance for Rectified Porcelain Tile would add up to about the grout joint width in the above example.

If you really want that small joint width, I'd recommend you start with a rectified tile and see just how well rectified they are before you commit to a joint width.

My opinion; worth price charged.

[MolsonB]

I'm doing a curbless linear drain heated shower, using all Schluter products, and want to double check on my math / application.

Joists = 9.5" i-beams, 16o.c.
Subfloor = 5/8" t&g plywood

I dropped the shower pan to be flush with the ibeams (5/8" down). I don't know why the house wasn't build on 3/4", but it is what it is. The foam tray is 7/8" but when you actually add the drain, the metal flange brings it closer to 15/16". I see in the Schluter install videos, when the subfloor is 3/4", they just build the transitions difference with thinset.

Since my subfloor is 5/8", thoughts are adding some 3/8 ply to bring me closer to the correct height. Since I'll be heating the floors, will be using ditra heat for the underlayment.

People say 3/8 ply is hard to find that is flat enough. I think going to 1/2" would be too tall? Thoughts?

Ofcourse using the Position of Underlayment.... as a guide.

[John Bridge]

Hi Matt,

Wouldn't 1/4 in. cement backer board get you close to what you need? 3/8 plywood is pretty much worthless.

[Davy]

Just so you know, Ditra heat is about 1/4 inch thick, plus a little more when thinset is added under it.