What are expansion joints and what are they used for?

According to the Portland Cement Association’s definition, expansion joints, also called isolation joints, are used to relieve flexural stresses due to vertical movement of slab-on-grade applications. An expansion joint is simply a buffer (usually made of wood, rubber or other material) inserted between two slabs of concrete. Properly installed, it will shrink and expand as the concrete moves, absorbing the pressure and stress of the movement before it starts cracking and crumbling the walls in your home.

Your driveway may already have an expansion joint but Street Creep may still occur if it not installed properly. Most contractors will pour the entire driveway and then while the concrete is still wet insert the expansion joint material into the wet concrete. If the depth of the concrete exceeds the width of the expansion material, there can be inches of concrete beneath the expansion material that renders the expansion joint useless. When the slab expands it will push the inches of concrete underneath the expansion material and in time push into your foundation wall causing damage to your home.

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