In modern masonry wall construction, integration of expansion joints (both vertical and horizontal) has become commonplace, but the rationale behind their width, placement, detailing, and maintenance is often misunderstood. With restoration projects and older wall systems it is often not clear whether expansion joints are needed and should be added as part of a restoration. Older structures in particular offer unique challenges. Damage of masonry wall systems can occur as a result of volume changes in the masonry materials despite the presence of expansion joints; this is frequently because joints are placed or installed inappropriately for the construction of the wall system, the particular wall geometry, or other factors related to the placement of joints designed to accommodate movement. This paper attempts to clarify and expand on the reasoning behind many of the standard guidelines commonly used for joint placement, size, and spacing. In addition, suggestions are provided for joint placement and detailing in several atypical situations, such as existing buildings, parapets, solid masonry wall systems, and window lintels. Factors leading to the need for expansion joints are reviewed, along with several lesser known concepts regarding expansion joint implementation. Also addressed are common problems with installation and maintenance of existing expansion joints.