An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials, to absorb vibration, to hold certain parts together, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of sidewalks, bridges, railway tracks, piping systems, ships, and other structures.
Throughout the year, building faces, concrete slabs, and pipelines will expand and contract due to the warming and cooling through seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced. The expansion joint can be as simple as a caulked separation between two sections of the same materials.
Expansion joints are used in pavements to provide for thermal and moisture-induced movement of the slab. However, these joints may also be required in areas or rooms subject to large temperature fluctuations. Designers should satisfy themselves that there is a definite need for expansion joints, thereby minimizing their unnecessary installation and the relatively wide gap required between panels.