Expansion joints in the field of tile floors are essential and required in order to accommodate building movements and to 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 width, locations, and frequency of field expansion joints are as specified by the design professional. Sealant type shall be specified by design professional and shall be compatible with other components in the system. This detail is based on Tile Council of North America (TCNA) method EJ171C. Details that show different or modified concepts or methods can be of equal validity and should not be excluded from consideration. This detail shall not be used for construction without the approval and signature of a licensed design professional. The person using this detail shall be responsible for its complete design and proper application.