It can be disturbing for a homeowner to realize that his residence has experienced foundation movement. Many homeowners have heard some of the horror stories about super expensive foundation repairs.
Foundation movement, almost all the time, is related to soil movement. Slab foundation stability depends on the support of the soil, so when the soil moves, most foundations (unfortunately) move differentially. “Differential Foundation Movement” means that the foundation moves more in one area than in another. The principle reason for this kind of movement is that the foundation is not rigid enough to overcome the movement of the soils. This type of movement creates sheetrock cracks, slab cracks, brick cracks, out of level doors and floors, etc. Unfortunately, this is the most common type of foundation movement in expansive clay soils.
The other kind of foundation movement (as opposed to differential movement) is the type where the foundation tilts (like when you pick up the edge of a card table). Tilting usually indicates that the foundation is well designed and constructed (it is rigid) but since the supporting soils below moved, the foundation moves as a unit. In these instances, a foundation that experiences tilt many times does not have a lot of cosmetic distress (sheetrock cracks, brick mortar cracks, etc.) or structural distress (slab cracks).
Neither type of foundation movement is pleasant to remedy. Both types typically require underpinning with piers. There are two reasons to install post construction piers:
1. To stabilize that area of the foundation from experiencing additional settlement, and/or
2. To attempt to make the foundation more level
Both of the above goals require using an experienced engineer, the right pier for the soil conditions and a reputable foundation repair contractor.
For more information on foundation movement, go to www.GeoDFW.com