Date: May 11, 2017
There are three truths in life… death, taxes, and concrete will crack. Joints are there to make sure we have control of where those cracks will occur.
Jointing concrete can be done in its plastic (wet) state with hand tools, but it can also be done with saws soon after the concrete sets.
We know scientifically based on the thickness of the slab the frequently the slab is going to want to crack due to the stresses of shrinking. If we know that concrete is going to naturally crack every 15’, we’re going to want to place the joints every 10’ so when a crack does develop, we’re creating a plane of weakness. The concrete is going to crack at the joints where it is easiest. There will still be a crack, but it will be hidden in the joint and much more visually appealing.
Rule of Thumb: The depth of the joints should be at least one-quarter of the slab’s thickness but not less than one inch.
|Pavement thickness, in.||Maximum Spacing, ft.|
|6 or greater||15|
The jointing pattern should be cut in squares. If you have irregular shaped panels or where angles are less than 45 degrees, you could use pre-cut wire mesh or fibers to control cracking. Fibers can help stop mini hair line cracks. As a crack starts to develop, it will stop when it reaches a fiber. Fibers are another way of enhancing the concrete and lessening the cracking problems that might develop.
Need help calculating your joints? If you use our Concrete Slab Calculator, a suggested measurement for your joints will automatically be calculated. You can also use our parking lot worksheet which has more information on jointing.