Joints in Concrete Slabs on Grade

Concrete expands and shrinks with changes in moisture and temperature. The overall tendency is to shrink and this can cause cracking at an early age. Irregular cracks are unsightly and difficult to maintain but generally do not affect the integrity of concrete.

Joints are simply pre-planned cracks. Joints in concrete slabs can be created by forming, tooling, sawing, and placement of joint formers.

• Contraction joints are intended to create weakened planes in the concrete and control the location where cracks appear
• Isolation or expansion joints separate or isolate slabs from other parts of the structure
• Construction joints are surfaces where two successive placements of concrete meet

•  Plan exact location of all joints, including timing of contraction joint sawing before construction
• Provide isolation joints between slabs and columns, walls and footings, and at junctions of driveways with walks, curbs or other obstructions

• Provide contraction joints and joint filling materials as outlined in specifications