This is why manufacturers only recommend a 1/3 offset pattern rather than a 1/2 offset pattern. They also recommend the use of medium bed mortar instead of thinset. Look on your tile manufacturer's website for guidance as to whether or not your installer followed their recommendations.

LWO, why would 1/3 offset be better than 1/2? Because there will be more of a discrepancy between the middle of the tile and the corners than 1/3 or 2/3?

SCpalmetto, it is a rectified tile. I think any slight warping in the tile is compounded by the fact that they used a very tight grout line so there's not much grout to help smooth the transition between tiles. Now I did ask for narrow grout lines, but I did not insist on a specific measurement. I believe they are 1/16. The head guy has come back to look at the finished product and he says it is acceptable and that it is the tile rather than the installation.

Livewireoak, I looked at the mfg website and I don't see any installation instructions. I'll keep digging. Tile is Roca stratos atmosphere. If the installer did not do what's recommended for the tile and we did specifically insist on 1/16, I think we have more ammo to get them to fix this at their cost.

I can't imagine why a rectified tile would dip at the corners unless it was installed incorrectly.

The TCNA industry standard term ''large format tile'' refers to any tile that is 16'' or larger in one dimension. That means a 16x16 or a 4x16 are both large format and follow under the TCNA recommendations for being set as large format. All large format tile will have droop. Because it's so large. It shrinks unevenly as it's fired. Rectified or not. That's why tile manufacturers will not warrant a random set, or a 1/2 offset.

Stacked, herringbone, or 1/3 offset are all fine, as that minimizes the high/low contact point between the ends and body. 1/32 is also the usual recommended minimum grout line, on a medium bed mortar, with a leveling system. Without the leveling system, 3/32 is as small as you'd want to go. That medium bed provides more support for the mass and makes it easier to level over the distance. Many leveling systems have also come on the market to help with the lippage issue, but they work best with the medium bed mortar and no less than 1/32 grout lines.

Lot's of installers have not kept up with the advances in tile manufacturing and are unfamiliar with the requirements for large format tile. And some don't want to invest in technology when they think they won't see a return in labor costs. Very few set out deliberately to do a poor job. They are just ignorant of the requirements. Or, they see themselves pricing themselves out of their market if the do a proper install.

Consumers have to realize that setting large format should be about twice as expensive as a standard 12x12 tile. Just the mortar is twice as expensive alone! Then add the extra time, and the investment into a leveling system. If you want a good job, you have to pay those additional costs. You won't be hiring the low bidder on the job and getting even a half decent job.

Here is a link that might be useful: Tuscan Leveling system.

ANSI and TCNA sort of go hand-in-hand.

ANSI A108 Grout joint size: To accommodate the range in facial dimensions of the tile supplied for a specific project, the actual grout joint size may, of necessity, vary from the grout joint size specified. The actual grout joint size shall be at least three times the actual variation of facial dimensions of the tile supplied. In no circumstance shall the grout joint be less than 1/16 in.

GROUT JOINT WIDTH PER TILEâÂÂS FACIAL DIMENSIONS 12â x 12â (nom.)

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Porcelain tile, rectified: Dimension can vary ñ .25% or .03 in. Allowable variation = 12 in. x .0025 = .03 in = approx. 1/32 in. Min. grout joint width = 3 x .03 = approx. 3/32 in.

GROUT JOINT WIDTH, LARGE FORMAT IN RUNNING BOND ANSI A108.02.4.3.8.1

For running bond/brick joint patterns utilizing tiles (square or rectangular) with any side greater than 15 in., the grout joint shall be, on average, a minimum of 1/8 in. wide for rectified tiles and, on average, a minimum of 3/16 in. wide for calibrated (non-rectified) tiles. The grout joint width shall be increased over the minimum requirement by the amount of edge warpage on the longest edge of the actual tiles being installed.

The following takes the recommended grout width (1/8th" for rectified) and adds to it for "warpage" (see above table) along the length of the large format tile.

20. 12â x 24â (nom.) Porcelain tile, rectified
    Grout joint width = 1/8 in. min., per ANSI A108.02.4.3.8.1

Longest edge warpage = 24 in. x .040 = .096 in. = approx. 3/32 inch vertical bow.

Min. grout joint width = 1/8 in. + 3/32 in. = approx. 7/32 in.

Here's a cartoon example of LFT with a 50% offset:

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33% offest:

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Hopefully that cutting and pasting resulted in a readable format...

Hollysprings and Mongoct, thank you for all of the valuable information. I wish I had asked this forum about the larger tile size before installation. Unfortunately the picture with the sad face is exactly what we have right now. We are still talking to the contractor about how to fix this.

Lesson learned - I will be sure to run my kitchen backsplash choice by this group to make sure we ask the right questions before it is installed. Thanks to everyone for your feedback.

Ditto on the thanks. I wish I had known about the 1/3 offset; no one ever mentioned this. I was able to talk with the tile importer and all he said was "use a 1/8" grout line unless you have an outstanding installer" - which it turned out we didn't. Our guy used the 5 spot thin set method to prevent lippage on our wall tiles which folks on the John Bridge forum say is a no no. Perhaps those of you in the know need to start a thread on why that setting method is unwise.

The setting method is unwise because it allows "voids" beneath the tile and makes them far more prone to breakage, particularly at the corners. Shoot for 90% coverage.

That type of tile requires a very flat floor, a medium-bed thinset, preferably a leveling system and a good mechanic.

Inspect the tiles before purchase. Place two of them face-to-face and try pinching the ends to check for "play."
There ARE tiles out there that are quite flat...but don't expect to find them for $1.50 a foot.....

Just in case your tile guy tells you that the 1/3 offset rule is not well known:

We recently tiled our shower/tub walls with 12 x 24" tiles and so did some research on dealing with large format tiles. The 1/3 offset thing came up right away. I believe the paperwork that came with the tile said the same thing, specifically warning against doing a running bond. I'll bet the folks at the tile supplier would have told him the same had he asked. Having agreed to set large format tile, it was totally reasonable to expect him to look up the how-to's.

It's also totally reasonably for him to have noticed there was a problem and stop the job to advise and/or research how to handle them.

Being in the tile business, he should be educated enough to know about lippage issues and techniques, to sort and calibrate his tiles first, laying large formats and not to proceed with a faulty job.

Ridiculous and irresponsible!

Thanks for all the follow up on this!

This tile wasn't expensive, but it wasn't $1.50 a foot either. Had I known to inspect for this problem, I would have selected a different tile.

I will ask the tile shop where they sourced the tile to give me the install instructions that came with the boxes of tile (if any).

Snookums2, that is what disappoints me the most with this situation. It was obviously bumpy looking and they just kept going. I think they should have looked at the tile before installing it and should have alerted us that the running bond would not produce a smooth surface. I would have gladly picked out a different tile at my cost if it could not be returned. Now I'm facing the cost of new tile and a redo install if he won't accept any responsibility with this result. This is something that will make me mad every time I enter the room so I know we have to redo it.

It's part of his job, not the layperson's. Post over on john bridge tile forum. They know the job of a professional. All this stuff is part of industry tiling standards, from checking the tiles first, to methods of handling the inherent issues In a tile due to the natural firing process, to acceptable tolerances in workmanship. Be informed for the upcoming discussion and for selecting your tile man for the next install.

There's always small claims court, where you don't need a lawyer. Just get really descriptive pictures and another professional opinion really helps (paid witness or affidavit).

Hopefully he will just admit he screwed up and not give you a hard time.

Good luck. These things are so difficult, frustrating and heartbreaking. And so unnecessary!