This is defined in the ansi american national standards institute standard a108 02 section 4 3 7.
Ceramic tile lippage standards.
Today however the ceramic tile industry has grown far more complicated as 12 in by 24 in 18 in by 18 in 24 in by 24 in and larger tiles are manufactured in abundance.
To address this on a practical basis some manufacturers recommend against any patterns with offsets in excess of 33 if the tile being used has an edge larger than 18 inches.
Rectangular tiles are harder to lay flat.
The standards state that a tile with a grout joint that is less than wide can have 1 32 of lippage in addition of what the actual warpage is of the tile being installed.
Materials environmental and workmanship section 4 3 7 lippage guidelines explanation and caution deals with what is allowable ceramic tile lippage and how to avoid excessive lippage.
The allowance for such warpage is also spelled out in a137 1 and would apply if your tiles are advertised as meeting that standard.
If the grout joint width is 1 4 or greater then the allowable warpage is 1 16 plus the allowable inherent warpage of the tile.
For your tile size and joint width presuming no offset the maximum allowable difference in elevation between tiles lippage is 1 32nd of an inch in addition to the inherent warpage of the individual tiles.
Too narrow grout joints.
Some types of tiles also curve as much as 0 5 the length of the tile such as polished porcelain tiles.
Narrow grout joints may look pleasing to the eyes but it increases the chance of tile lippage.
For large tiles exhibiting the maximum allowable warpage 50 offsets are guaranteed to exhibit lippage.
A bad batch of tiles tends to show lippage more.
Long narrow tiles are used.
American national standards institute ansi a108 02 2013 general requirements.
Lippage is the vertical displacement between two adjacent tiles of a ceramic glass or stone installation.
Lippage refers to differences in elevation between edges of adjacent tile modules the ansi standard notes that the perception of lippage is influenced by many factors such as.
There are tolerances for tile lippage.
This is assuming that the warpage of the tile is within the standard s acceptable range for that type of tile.
It states for grout joints that are less than 6 mm 1 4 in wide.
When excessive this can lead to numerous problems ranging from chipped edges to snagged furnishings and appliances to safety hazards.
The ansi a108 02 standards say that acceptable lippage for floor tiles with a grout joint width of 1 16 to less than 1 4 is 1 32 plus the allowable inherent warpage of the tile.
Some joints are 1 8 others are 5 8 with a lot of lippage some even at 6 credit cards deep.
They are telling me it is within the standard based on the tile warpage.