Generally speaking, defective tiles are tiles that do not pass inspection for many reasons when evaluated at the factory once they have been manufactured but before they are shipped to the public. Tile can be defective for having too much size variance tile to tile within the same lot. That also applies to excess warpage or thickness. Tile can be defective for being produced with facial anomalies like chips or pits. Here in the United States, the manual the sets the standards for the manufacture of ceramic tile is ANSI 137.1. Unfortunately that manual has not been republished in the last 10 years making it obsolete. We experts still quote from it, however, as it is the only national standard available. Internationally, the standard manual is ISO 13006, 1998.

Both of these manuals dictate the qualities that tile should possess to be acceptable for sale and use. Interestingly, the testing that tiles undergo is very similar between the ANSI and ISO manuals.