2.9 : Movement Joints in Buildings

Movement joints in buildings are essential design elements that accommodate inevitable motions caused by various factors such as temperature changes, moisture content variations, and structural deflections. These motions, if not considered in design and construction, can lead to unsightly or dangerous damage. Movement joints are incorporated in different forms to manage these stresses and allow materials to move without causing distress.

The simplest type of movement joints, working joints, are integrated during the construction process. Examples include shingled roofs and wood bevel siding, which allow for thermal and moisture movements. Structure/enclosure joints separate structural from nonstructural elements to prevent load transfer that could cause damage, such as deflection tracks in metal-framed walls or soft joints under shelf angles supporting masonry veneers.

Isolation joints are used to prevent interference between materials that need to move independently, typical in renovations or where concrete slabs meet structural elements. Control joints create predetermined lines of weakness to direct cracking in a controlled manner, commonly seen in concrete sidewalks and plaster walls. Expansion joints accommodate material expansion and contraction, evident in brick walls and curtain wall systems.

Lastly, building separation joints divide complex structures into segments that move independently, categorized into volume-change joints, settlement joints, and seismic separation joints, each addressing specific structural movement challenges.