Many installers have had customers who have seen a tile installation in a magazine or brochure, which is exactly what they want in their homes. Unfortunately, the look they want to achieve may not be possible using the tile that has been selected.
Depending on the type of tile selected and its dimensional sizing, if tested to the American National Standards Institute (ANSI) specifications, it may be contained in the A137.1 document for the production of ceramic tile products. Under A137.1, tiles fall under one of three categories: natural tiles, which are packaged directly after manufacturing and are not sorted by size; calibrated tiles, which are sorted after production to meet a specific range of size; and rectified tiles, which are taken from the production line and mechanically finished. This process grinds the edges of the tile to achieve a more precise facial dimension. The grinding makes the sides parallel to each other and sized to a specific dimension, such as a large format plank tile, as seen in the attached photo.
If the customer selects a calibrated tile—which legally can contain various sized tiles in the same box—for the project and requests that the grout joint be the thickness of a credit card (1/32"), the installer may have a very difficult, if not impossible, task. Using such a narrow grout joint with tiles that vary in size could result in two larger tiles side by side that actually touch each other with no grout joint, while two smaller tiles side by side could show a grout joint of over 1/8" or more (four times the requested 1/32"). However, if the customer selects a rectified tile, the opportunity for success is much greater.
This is where another ANSI specification, A108.02-4.3.8, defines the required minimum 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 the facial dimensions of the tile supplied. Example: for tile having a total variation of 1/16" in facial dimensions, a minimum of 3/16" grout joint shall be used. Nominal centerline of all joints shall be straight with due allowances for hand-molded or rustic tiles. In no circumstance shall the grout joint be less than 1/16".
As per the example, a tile with just a 1/16" variation in size requires that the grout joint be 3/16", which is significantly wider that the 1/32" grout joint the consumer desired. Installers need to know these specs and use these details to their advantage. Allowing a consumer to dictate the grout joint size without regard to these industry guidelines can lead to a disaster. Know the rules and eliminate these problems from your jobsites.