QUESTION
What are the tolerances for 12″ x 12″ tile for “square” and size consistency? We have a project that we could not delay and are trying to recover lost production costs. The tile is not adequately square, flat, or sized consistently.
ANSWER
The American National Standard Specifications for Ceramic Tile ANSI A137.1 contains the manufacturing specifications for ceramic tile. The specifications vary depending on tile type.

The first thing you need to do is determine is whether the tile you are installing has been manufactured to meet or exceed the Nominal Size and Wedging specifications of ANSI A137.1 for the type of tile (Pressed Floor Tile or Porcelain Tile) and its sub-category (Natural, Calibrated, or Rectified). You can check with the tile distributor, manufacturer or the manufacturer’s Technical Data Sheet or other supporting documentation to determine if the tile was manufactured, tested and labeled to meet or exceed these ANSI A137.1 specifications. The tile you are installing may or may not meet these specifications – there is no requirement for a tile manufacturer to make any or all of their tile to meet these specifications.
ANSI A137.1 Table 8 details the requirements for Pressed Floor Tile and Table 10 details the requirements for Porcelain Tile. Each table identifies the specification ranges for the subcategories of Natural, Calibrated, and Rectified for Pressed Floor Tiles and Calibrated and Rectified for Porcelain tiles. Within each sub-category, there is a specified tolerance range for Nominal Size and Wedging. Nominal size is self-explanatory. Wedging is essentially how square a tile is.
Please note that although percentages are listed for Pressed Floor Tile and Porcelain Tile, the variations cannot continue to increase as tile size increases. The measurements shown in inches are the not to be exceeded caps for the measurement indicated.
For Pressed Floor Tile, the ranges are:
Natural
• Nominal Size Minimum: -4.00%
• Nominal Size Maximum: 4.00%
• Wedging Minimum: -1.00% or -0.12″
• Wedging Maximum: 1.00% or 0.12″
Calibrated >/= 6″ tile size
• Nominal Size Minimum: -3.00%
• Nominal Size Maximum: 3.00%
• Wedging Minimum: -0.50% or -0.08″
• Wedging Maximum: 0.50% or 0.08″
Rectified >/= 6″ tile size
• Nominal Size Minimum: -3.00%
• Nominal Size Maximum: 2.00%
• Wedging Minimum: -0.25% or -0.03″
• Wedging Maximum: 0.25% or 0.03″
For Porcelain Tile, the ranges are:
Calibrated >/= 6″ tile size
• Nominal Size Minimum: -3.00%
• Nominal Size Maximum: 3.00%
• Wedging Minimum: -0.50% or -0.08″
• Wedging Maximum: 0.50% or 0.08″
Rectified >/= 6″ tile size
• Nominal Size Minimum: -3.00%
• Nominal Size Maximum: 2.00%
• Wedging Minimum: -0.25% or -0.03″
• Wedging Maximum: 0.25% or 0.03″
ANSI A137.1 Tables 6, 7, and 9 include the specifications for Quarry Tile, Mosaic Tile, and Glazed Wall Tile.
There are a number of other specifications that tile can be manufactured to and tested to meet. I suggest purchasing a copy of ANSI A137.1 so you will have access to these numbers when you have questions. A copy can be purchased from the TCNA website at https://www.tcnatile.com under Publications, or here: https://tinyurl.com/yc5v954j