Expansion joints in the field of tile walls are essential and required to accommodate building movements and to prohibit cracks in the substrate from telegraphing to the tile finish. This detail illustrates a movement joint in the tile continuing through the backer board behind it. The Backer rod in the joint prevents three-sided adhesion of the sealant. Joint width, location, and frequency of field expansion joints are as specified by the design professional. The sealant type shall be specified by a design professional and shall be compatible with other components in the system. This detail is based on the Tile Council of North America (TCNA) method EJ171K. 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.