As concrete settles, it can experience random cracking. However, joints are intentionally placed in concrete slabs to help reduce and control random cracking. There are typically three types of concrete joints available: expansion, construction and contraction. Before you tackle your next large concrete project, familiarize yourself with proper jointing tips and techniques.
Contraction joints are placed specifically to reduce cracking. The joint should have a depth of 1/4 the thickness of the concrete to ensure a weak enough area through which the concrete can crack. For example, a 4”-thick driveway should be cut or jointed to a minimum depth of 1”.
Contraction joints should be placed at regular intervals. The rule of thumb is that for every 1” in slab depth, there should be 2-1/2 times the depth expressed in feet between joints. For instance, a 4”-thick driveway should be jointed at least every 10’.
Expansion joints are used to separate slabs and concrete from other parts of a structure. These joints allow movement between the structures to help minimize cracking.
If you are using expansion joints, they should be placed where the fresh concrete abuts existing concrete. For example, expansion joints should be placed between garage slabs and driveways or driveways and sidewalks. This keeps the fresh concrete from bonding to the existing concrete, allowing the wet concrete to shrink without restriction.
Construction joints are used when two areas of concrete meet. These are typically placed at the end of the day and are typically designed by a structural engineer.
By properly jointing your concrete, you can create a beautiful finished look. Use our concrete calculator to determine how much concrete you need for your next project.