Are you using expansion joints on your commercial roofing projects? They are most commonly required at locations where differential movement is predictable. Differential movement occurs where adjoining materials exhibit different rates of dimensional change in response to environmental or load changes, which results in excessive stress between the dissimilar materials.
The more common locations where expansion joints are positioned to relieve expected stress are:
- Where the materials of a framing system change, such as from steel to concrete
- Where deck or beam systems change direction
- Where deck materials or characteristics change; for example, from steel to wood or from cast-in-place concrete to pre-stressed concrete
- Where adjoining structural systems differ in flexibility, such as where a single-story building joins a multi-story building or one with fixed column bases joins one with hinged column bases
- Where dissimilar settlement is expected, such as at additions or where buildings on piles join those on spread footings
- Where the roof deck is not supported by walls
- Where ambient or interior temperatures vary, such as at canopies or between a freezer building and adjoining offices
- Where exposed concrete or wood framing is subjected to considerable and fluctuating moisture differentials, such as between classrooms and a swimming pool