The most common way to repair foundation cracks in concrete slabs and walls is to fill the crack with epoxy, a synthetic resin. Epoxy is known for its toughness, superior adhesion, low shrinkage and resistance to chemicals and water.
Before the epoxy is injected, the surface surrounding the crack needs to be prepared. This involves cleaning the area and removing any loose material with a chisel. After the crack has been filled, staples are placed across the crack for additional support and stabilization. Repairing the crack with epoxy will prevent it from increasing in size and prevent moisture from penetrating the concrete.
Foundation cracks can also be closed and prevented from moving by installing carbon-fiber Kevlar straps. These lightweight straps have considerable strength and are easy to work with. They are used along with epoxy injections to repair walls that have horizontal cracks. Horizontal cracking is usually an indicator of too much weight against the wall. This type of cracking is extremely serious because it can eventually lead to the wall’s collapse.
In addition to epoxy and strapping, underpinning may also be necessary to resolve foundation settlement and cracking problems. The purpose of underpinning is to increase the depth or width of the foundation so it can better support the structure’s weight. When a building is too heavy for its foundation, not only will the foundation crack, the walls of the structure can begin to bow. Underpinning distributes the weight of the structure more evenly and provides better support for the building.
Underpinning is also used for homes constructed on expansive soil, like clay. When clay gets wet it swells, and when it dries, it contracts. These moisture fluctuations lead to foundation settlement, cracks and other types of foundation issues.