What is the most likely cause of vertical cracks in a poured concrete foundation?

Vertical cracks in a poured concrete foundation are primarily caused by the shrinkage of the concrete as it cures. When concrete is mixed, water is added to achieve the desired workability. If there is excessive water in the mix, it can lead to increased shrinkage as the concrete dries and hardens. This shrinkage can create tensile stress within the concrete, leading to the formation of vertical cracks, particularly in the walls of the foundation where the concrete is less restrained.

Understanding this phenomenon is essential for identifying potential issues in a foundation's integrity and can guide remediation efforts. While other factors like differential settlement and poor drainage conditions can contribute to foundation issues, they are more commonly associated with horizontal or diagonal cracking rather than purely vertical cracks. Therefore, recognizing shrinkage as a major factor helps in addressing the underlying causes of such defects in concrete foundations.