Challenges of Setting Long Lengths of Tile
I was called out to inspect various tile and grout issues on this job and write a technical report for the general contractor, as his current tile contractor had abandoned the job.
The tile on this wall looks rippled. There is lippage on this installation. “Lippage” is defined in the ANSI (American National Standards Institute) standard A108.02, Section 4.3.7: "Lippage refers to differences in elevation between edges of adjacent tile modules." In other words, it refers to tiles that are out of plane with each other by more than a dime’s thickness.
This is not the fault of the installer; the actual tiles are curved in the center, and when you stagger them above and below each other the curve is accentuated by the natural crown of the tile. Lippage occurs on stagger-set installations because the ends of the tile are flatter, and adjacent to the center crown of the tiles above and below it.
Also, lippage tends to be a common problem when installing plank-length floor tiles as well. Examples of this would be 6x24", 6x36", and 6x48" sizes, usually finished to look like wood.
One way to lessen the lippage is to stagger set in thirds. This photo shows a stagger set in halves. Lippage occurs with a stagger set layout in thirds, but it will be greatly reduced.