When the concrete slab is poured for your new house, you may think that it is all one solid slab, with no cuts or anything similar. However, that's really not true. After the slab starts to harden, the contractor will cut in something called control joints.
Control joints are also called contraction joints. They are seams that are cut into the concrete that allows for expansion and contraction of the concrete in the heat and the cold. The joints aren't cut into the concrete randomly, they are placed in particular spots so that the joints will be most effective.
Benefits of Control Joints
The biggest benefit of a control joint is the fact that controls where the concrete may crack. Expansion and contraction of the concrete can cause cracking. Cracked concrete can cause significant problems, including letting in water and weakening the structure. The control joints will make sure any cracks happen in a particular spot. That makes sure that cracks don't happen in any vital areas.
Control Joint Creation
Control joints can't be cut into the concrete immediately. The contractor has to wait until the concrete starts to harden. That can be as short as an hour depending on things like the weather and how thick the slab is. While the joint needs to be cut into the concrete when it's hardening, it's important to make sure that the concrete hasn't completely set before the joints are cut in. That's because the concrete could start to form its own joints, or cracks, before the joints can be created to control where any cracks could form.
Control Joint Placement
The control joints aren't cut all the way through the concrete slab, that would cause problems with the structural integrity of the slab. Instead, they are generally cut about 1/4 of the way through the concrete. That's deep enough to allow for the contraction and expansion and control where any cracks go. Since cracks will follow the weakest point, adding in the control joint creates the weakest point where the contractor wants it to be. When control joints are cut into the slab, the formula is usually 2 or 3 times as far as the slab is thick, in inches. For example, a slab that is 5 inches thick will have control joints placed every 10-15 feet.
While you may think that you want your concrete slab to be all one solid piece, that would actually cause more problems. You want the contractor to cut in control joints so that the slab will maintain its integrity. Contact a business, such as Premo Concrete LTD concrete work, for more information.
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