Why Does Concrete Crack?

The saying goes, “It’s not if your concrete is going to crack, it’s when your concrete is going to crack”.

The Truth

There is not much you can do to get around it, all concrete is more than likely going to crack over time. If your concrete contractor tells you otherwise, they are either ignorant or lying. Cracking is just the nature of concrete.

This article, however, is not meant to scare you away from choosing a concrete slab for your home! Instead, we wish to further your concrete knowledge to minimize potential cracking and help you understand that even hiring the best concrete contractor in the world or paying an engineer to calculate a design, may still lead to some issues with cracking.

Common Causes of Concrete Cracking

There is no one reason that concrete cracks, but instead there are a multitude of potential causes.

1.) No Crushed Stone Base

  • Without a crushed stone base, a concrete slab is more susceptible to forces from the environment such as soils movement or water washing away the subgrade.


crushed stone base fig TriStar Concrete



2.) Missing Control Joints

  • Control joints are the lines that are cut or tooled into the slab when the concrete is placed. These joints don’t exactly prevent the slab from cracking, instead they aid in planning where the concrete will crack.

control joint fig TriStar Concrete


 3.) Lack of Construction Joints

  • Construction joints are used to connect two separate slabs. Without construction joints, the two slabs could slip and push against one another. This can cause cracking and tripping hazards.

construction joint fig TriStar Concrete

4.) Wrong Concrete Mix Design

  • Everything from water content, air, and temperature has to be just right when it comes to your concrete mix design. Fortunately, modern concrete mix designs supplied by knowledgeable companies rarely lead to cracking.

5.)Improper Curing

  • Curing is the process of maintaining an adequate water cement ratio and temperature in concrete from the time the concrete is poured, and until the concrete has met the specified strength of the concrete mix design. Inadequate curing will ultimately lead to weak concrete that is more susceptible to cracking by allowing the concrete to dry too quickly.