Foundation Cracks in Poured Concrete Walls

Crack Types

Foundation cracks exist in three basic forms: settlement, shrinkage and expansion. Each can occur to poured concrete wall slabs. For the most part, the only type of significant worry is an expansion crack. The other two, settlement and shrinkage, are fairly minor cracks that are not entirely unusual to find in homes.

A settlement crack regularly results from inadequate site planning, such as uncompacted fill dirt or lack of foundation wall reinforcements, notes the InspectAPedia website. The crack starts out small and grows longer and wider with time. A settlement crack is typically wider at its highest point and curves toward its lowest point, and can be viewed from both the interior and exterior sides of the wall. It's possible to see several settlement cracks in a concrete wall slab. A certain amount of settlement cracks are customary to find in homes, especially in newer ones. However, if you notice cracks at both ends of a concrete wall, the cracking might be caused by shifting ground, like a sink hole, that is impacting the structure's integrity. Contact a contractor or structural engineer who can measure the wall slope and evaluate the problem more thoroughly.

Most often shrinkage cracks happen as poured concrete slabs cure and harden. A shrinkage crack appears as either a diagonal or vertical crack of near even width. The cracks might also narrow to an asymmetrical hairline and end. Shrinkage cracks are caused when the concrete wall retreats from the foundation wall and usually occur because control joints were omitted from the wall floor design. They frequently appear beneath a window or above a doorway, but also can come about in the middle of a slab. Shrinkage cracks normally bear no structural consequence unless they enable water to seep through the wall, in which case they need to be sealed.

Expansion cracks frequently appear in a vertical pattern near the wall's corners, although an expansion crack can also be horizontal. Extreme heat from sunlight beaming on the concrete wall, such as the case with a slab home, or the earth's natural heat, as the case with a basement wall, coupled with repeated moisture exposure over time can make the wall expand. Conversely, periods of cold temperatures and dryness can result in the gap contracting. These cracks must be repaired immediately to prevent them from spreading. In certain cases, they can allow water to enter the home, damage windows and doorways and jeopardize a structure's integrity, thus making the building unsafe. Contact a licensed contractor or structural engineer to further assess the damage.