Expansion joints in the field of tile floors are required to accommodate building movements and prohibit cracks in the substrate from telegraphing to the tile finish. This detail illustrates an expansion joint in tile installed over an unbonded reinforced mortar bed on a concrete floor. A cleavage membrane allows independent movement between the concrete substrate and the tile assembly. The expansion joint goes all the way through the mortar bed. A bond coat of modified cementitious mortar is used to adhere the tile to the cured mortar bed, and a waterproof membrane may be specified over the cured mortar bed. The design professional specifies the width, locations, and frequency of field expansion joints. Sealant type should also be specified by design professional and must be compatible with other components in the system. This detail is based on Tile Council of North America (TCNA) method EJ171C.