Lippage unfortunately occurs when one tile edge is higher or lower than the adjacent tile. This topic continues to receive a significant amount of coverage in written documents as well as everyday conversation. The reason lippage is constantly being discussed is because it occurs entirely too often.
According to the chart on “Flatness and Lippage” found in the TCNA Handbook, lippage can be measured and has an allowable limit. For pressed floor and porcelain tiles, of all sizes, with a grout join of 1/16" to less than ¼", the allowable lippage is 1/32".
Lippage can occur in tile installations where an offset pattern is required using tiles that are 15" or longer and may have one or a combination of these situations present; the floor substrate is not flat to 1/8" in ten feet, which is required under the ANSI Standard A108.02 – 126.96.36.199.1; the inherent warpage of the ceramic or porcelain tile causes the tile to bow up in the middle, which is controlled under the ANSI A137.1 Standard; the offset is greater than 33% as found in the ANSI A108.02 – 188.8.131.52, or installer error occurs.
Additionally, lippage causes three hazards to occur. The first is that one or more of the above mentioned standards has been violated and can be grounds for the job to be rejected. The second is that a serious injury may occur if someone trips on the high tile. In this case, the installer is responsible if someone falls and could be involved in an expensive lawsuit. And finally, it looks really bad. The first two items are extremely important and are not meant to be minimized, but the last one is something that gives the entire tile industry a black eye.
As seen in the attached photo, the lippage is evident in a commercial dining area where the movement of the chair leg across the high tile edge has caused it to chip in several places. The real problem here is that when a potential consumer views this problem in a public area, he or she may believe that all tile installations will do this and decide they will never use ceramic tile in their home.
If this occurs, the entire tile industry will suffer and the next time this consumer needs a product to cover the floor or the wall, they will pick something else.
By the way, a couple of facts about this installation: The woodgrain plank was a 6"x 36" calibrated (not rectified) tile with a 6" (16.6%) offset, which can help eliminate lippage. The grout joint about a 1/16", which is less than the required joint size of 3/16" for a calibrated tile under ANSI A108.02 – 184.108.40.206, and the lippage was just over 1/16" which is double the allowable 1/32".
Had the installer used the ANSI “tools” that are listed above, the lippage most likely would not have occurred and the tile industry would not suffer any ill effects.