Slabs on grade may contract, expand, or settle under service conditions. If these movements are restrained, slabs can crack or buckle. Isolation joints in interior slabs on grade allow horizontal and vertical movement between the slab and adjoining structures such as walls, columns, or equipment bases. Expansion joints are recommended for use to separate sidewalks from driveways, driveways from garage slabs, pavements from bridges or other fixed objects, and parking lot slabs from light-standard foundations, planters, and buildings.