Foundation settlement and movement can lead to serious structural issues, such as sinking foundations. While you can repair minor shrinkage cracks with patches or sealants, vertical foundation movement, where the foundation sinks into the soil, is a structural issue. These cracks may be caused by soil settlement, frost heaves or sudden forces, such as earthquakes or floods. Structural damage requires a professional who will typically use one of two methods to repair your foundation: slabjacking or piering.
Deciphering the Cracks
Foundation cracks are often the first indication for homeowners of a foundation problem. Hairline cracks in a new foundation are usually shrinkage cracks, which are not a structural issue. However, if you have stair step or stepped cracks in a concrete block wall or brick wall foundation, some type of settlement or heaving has occurred. Vertical or almost vertical cracks in poured concrete or concrete block foundations are also a sign of structural problems. If these cracks are wider at the top, it means that one end or both ends of the foundation have dropped, or the middle of the foundation is heaving or rising. If the cracks are wider at the bottom, it means one or both ends are rising, or that the middle is sinking. Cracks that appear horizontally in the joints of a concrete block foundation are a sign that the pressure of the soil has bent the wall and the foundation is failing. This is a serious structural issue that should be addressed by a professional. Any cracks in your foundation that are larger than 1/4 inch, or that increase in size, should be inspected by a professional.
Masonry Patches and Sealants
If your foundation has cracked due to shrinkage, the typical repair uses patches or sealants. Shrinkage cracks in the corners of a slab foundation are common and are typically caulked or filled with hydraulic cement that expands as it dries. Other shrinkage cracks are repaired using a variety of products, such as masonry repair epoxy or sealants. While this type of crack isn’t typically an indication of a structural issue, you should seal it to prevent water from entering the foundation.
Contractors sometimes repair sinking foundations using a process called slabjacking, filling the space under the slab so that it floats back to its original position. This involves drilling strategically placed holes into the base of the concrete slab and using portable pumps to fill the holes with a mixture of cement, fly ash and other additives. Slabjacking is typically a professional job because it requires specialized equipment and knowledge.
Piering is also called piling and uses different types of steel pipe pilings to correct foundation settlement. Push piers are sections of galvanized or epoxy-coated steel pipe driven deep into the ground using a hydraulic ram. Helical piers use screw-like piles with steel shafts. To install a helical pier, a trench is dug around the foundation and a helix plate is attached to a steel shaft that is driven into the soil. Hydraulic jacks are attached to both types of piers to raise the foundation, and then the piers are bolted or welded to wall brackets on the foundation to lock it in place. Drilled bell piers repair the foundation in a slightly different way. This type of pier consists of a belled shaft drilled through the foundation. The belled shaft is then filled with concrete to provide a new, solid support system.
- Concrete Network: Foundation Repair: Concrete Foundation Repair
- Concrete Network: What is Slabjacking
- Concrete Network: Using Piers to Fix Concrete Foundations
- Ask the Builder: Foundation Crack Illustrations
- Quality Waterproofing: The Different Types of Foundation Repair Strategies
- Inspectapedia: Foundation Repair
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