If you're in the middle of a job where you're having a concrete foundation laid, you need to make sure your contractor knows the importance of having control joints done immediately after setting by an experienced professional. If contract joints aren't already present in the foundation plan, discuss with your contractor where they'll go. Here are three reasons it's necessary to get your control joints cut well.
1. Control joints help relieve strain in the concrete.
Control joints, created by cutting partway into the concrete in a straight line, allow the concrete foundation to shift slightly more than it would otherwise be able to. This means that when temperatures change, the concrete can swell or shrink a tiny bit without causing damage to itself. This is important because if the control joints aren't there, these changes in temperature can cause random cracking to occur.
2. Control joints are only effective if done on time.
One of the most major shrinkages that will occur during the concrete's working lifespan happens immediately. While drying, the volume of the concrete diminishes slightly, meaning that it will tighten and stretch in all directions. So you need to have the person who's going to place the control joints ready right away if it's going to get done in time. If the joints aren't cut within the first twelve hours or so (or sometimes even less), cracking may occur before joints are put in, making them less effective and superfluous.
3. Joints keep cracking controlled.
Although the control joints don't actually stop concrete from cracking, they can help you direct the cracking along the better courses. For example, you can direct it away from areas that have tile or laminate flooring, which may not stretch to accommodate cracking as well as carpeting will. In addition, the joints help the concrete surface look more attractive, which is important if you're going to use it as an unfinished floor rather than installing carpet. This is because the joints cut one-quarter of the way through the slab to "weaken" it in a straight line, encouraging cracks to take place down in the interior where it's weakened rather than cracking all the way through the slab and showing up on top.
As you can see, control joints are an important part of keeping your concrete's behavior compliant with your expectations. If you use steel to reinforce your concrete control joints won't be necessary, but in all other cases you'll need to plan for them well in advance to make sure you get the best usage out of them. Contact a contractor, like National Concrete Cutting, for more help.