An excellent quality tile installation will stand the test of time and remain a shining example of the beauty and durability of ceramic and porcelain tile; however, when other installations of lesser quality exist, the tile industry gets a black eye. The tile installation in the below image is an example of a whole host of installation failures that do not follow the American National Standards Institute (ANSI) requirements.
ANSI A108.5 – 2.2.2 Apply mortar with flat side of trowel keying in with pressure, over an area no greater than can be covered with tile before the mortar skins over. Cover surface uniformly with no bare spots and with sufficient mortar to ensure a minimum mortar thickness of 3/32 in. (2MM) between tile and backing after tile has been forcibly embedded. Tile shall not be applied to skinned-over mortar.