It's common to find different sizes within a manufacturing run. Manufacturers typically box tiles with lot numbers on boxes, and sourcing tile from the same lot *may* help reduce getting different sizes. "Rectified" tiles are cut after manufacture, so are more uniform in size. Rectified tiles still need to be sorted by lot and checked, as described below.
But, we're not done yet!
Once the installer gets the boxes on the job, they need to open a representative number of boxes, pick out some tiles, and stack them up on edge side by side to compare sizes. After stacking and checking a few, rotate them and check sizes in the other direction. There is typically some difference in sizes.
The installer needs to come up with the differences in tile sizes to determine grout joint width. The **minimum** grout joint size = 3x the difference in tile sizes. For example, if the differences are slight, say 1/16", then the **minimum** grout joint size is 3/16".
There is typically some differences in tile sizes with manufactured tile. Planning for this is what makes the jobs come out looking just fine. Specifying grout joint width, before doing all the above is a recipe for disaster.
