Expansion joints are specified for specialized projects in which common sealants would not be successful. When expansion joints are used, the designer or consultant must understand and correctly calculate the anticipated movement of the joint where it is installed. This course explains several items related to expansion-joint specification such as thermal expansion, categories of roof joints and the evolution of expansion joints, and key design considerations. Typical problems that occur when using expansion joints are also revealed. The presentation also explains how to properly evaluate different methods of waterproofing of expansion joints.