“Crackin’ happens over enough time or after enough abuse in one spot,” A.J., a contractor with a crew of five in Denver, CO, said. “That’s why we cut in control joints.”

He now is trying to educate a former customer on why the crack in their concrete patio is a foot and a half, not the entire width of their patio – thanks to his control joints he had put in using a concrete cutting saw.

One way to explain that cracks might happen (after whatever amount of time that you guarantee your work) up front with customer is in the review of the draft plan for the driveway. Show where the control joints are, and explain their purpose.

Concrete is a material that expands when it gets wet and contracts when it dries again. Then you add in weather changes with water freezing overnight. There’s a reason both potholes and the saying “concrete never cures” exist.

Control joints are either formed as the slabs are made or cut in with a concrete control joint cutting saw – such as once of these – after the concrete has cured, saving time and providing a cleaner aesthetic value in the long run.

Concrete control joints serve as “fire breaks,” much the same as when forest firefighters cut and burn down a clearing around a forest fire, so it reaches a point at which there is insufficient fuel for it to continue, and its path is broken.

A control joint that has been made using a concrete cutting saw or traditional method can often dissipate the energy of the crack downward along it’s line, preserving as much of the surface area aesthetics as possible.

In almost all cases, the control joint contains the crack from going beyond its boundary line, which means only that section of the concrete needs repaired, not the entire patio, driveway, garage floor, etc.

The more the control joints, the less distance a future break can travel, but of course the number of joints will need to be balanced with other factors of the project, such as where slope changes occur on a driveway that needs to be a convex curve of slabs up a small hill.

While some might think they’re saving time or having a cleaner look with almost no control joints, when a crack does occur it’s a bigger, more costly problem. Always follow the local codes, where they apply to control joints. If you cut a lot of them, it might be time to invest in your saw.