Our experience is that cast in place concrete has been used for foundation walls in this area of the country since around the 1920’s. It is generally a very durable material which can be formed and cast into almost any configuration. It’s ability to support or resist compressive loads far exceeds what it can support or resist in tension. If concrete is used in construction where tension stresses will develop beyond what the concrete alone can safely resist, steel reinforcing bars are installed to take up those tension stresses.

Generally speaking the tension stresses which develop in an 8′ tall concrete foundation wall, 8″ thick, do not exceed what the concrete alone can safely resist. The tension stresses being referred to here are the stresses at the interior face of the foundation wall which result as the foundation wall resists the lateral or inward soil pressure from the outside. This is assuming that the foundation wall is properly secured along the top by the floor framing and along the bottom by a concrete floor slab. In the case of shorter foundation walls around a crawl space with a dirt or gravel floor, the lateral or inward soil pressure is much lower and the bottom of the wall is restrained by the footing under the foundation wall being embedded into the soil.

One of the most common problems we find with cast in place concrete foundation walls is inward rotation or leaning caused by inadequate lateral support along the top of the wall. Some early signs of foundation wall movement include diagonal cracks at the corners of the foundation wall with a vertical crack typically located near the center, and the foundation wall is out of plumb or leaning into the basement or crawl space. There are several scenarios which can result in a lack of lateral support along the top of the foundation wall. The most common is a failure of the connection between the top of the foundation wall and the floor framing. Other possibilities include a failure of the beam line to properly restrain the foundation walls, the foundation wall running parallel to the floor framing with no provision for bracing the foundation wall, or instability caused by the construction of a framed knee wall on top of the concrete wall.

A less common problem is general deterioration of the concrete which is typically found in older foundation walls.

Another less common problem is horizontal cracking which is typically caused by deterioration or rusting of reinforcing steel bars. This can be a significant problem because the ability of the concrete wall to resist the lateral or inward soil pressure is compromised by the separation of the wall along the crack line(s).

A very common occurrence with concrete foundation walls, and concrete floor slabs, is the development of shrinkage cracks. I use the word “occurrence” and not “problem” because shrinkage cracks are a normal and expected occurrence. They only become a nuisance if they leak water, which can be easily remedied with epoxy or urethane injection. In foundation walls shrinkage cracks are generally, not perfectly, vertical and 1/8″ in width or less. They typically develop at approximately 10 to 15 feet on center along the length of a wall, in corners, and at locations where the cross sectional area of the concrete wall has been reduced by penetrations such as window openings and beam pockets. The number and size of the cracks may vary depending on how much water was in the concrete mix at the time it was placed or poured. As the water content increases so do the number and size of the shrinkage cracks.