A pier and beam/crawl space foundation is just what it sounds like. It is a design where a structure sits atop beams, which in turn rest upon piers or stem walls.
The piers typically sit on concrete footings, and are evenly spaced underneath the structure to balance the load. The weight of the structure is transferred to the beams, which transfers it to the piers, and so on.
This design includes a crawl space, an open area below the floor, so access is available if issues arise that require repair. Because the pier and beam/crawl space foundations are made of wood, they are susceptible to lumber deterioration over time. In addition, the footings that provide support are generally shallow — and therefore subject to substantial soil movements (relating to changes in the soil’s moisture content).
These are not the only problems associated with crawl space/pier and beam structures, but they are the most prevalent. The “good” news about repairing and leveling a pier and beam foundation is that it is adjustable by nature of the design and the work can usually be done without relocation of tenants or furnishings.
Since this system is considered a shallow foundation, it is subject to the effects of soil movement. As soil shifts, the structure becomes unlevel and distorted. This movement can occur over long periods of time, or sometimes very quickly.
Here is what we do:
When a crawl space/pier and beam structure experiences deterioration, it is time to replace the wooden members. Typically though, not all of the floor framing system requires replacement, but may be limited to only affected areas.
Replacement of the structural members can often be very complex, and can require temporary shoring to support the structure while damaged materials are being replaced.
Inexperienced companies often choose to add on to the deteriorating members instead of removing and replacing. This can lead to improper load distribution and support of structural members and should be avoided.
Once all deteriorated lumber has been removed and replaced — and steps have been taken to control the soil’s moisture content — the structure can be re-leveled, or “shimmed.”
Perfect results, in terms of floor flatness, are not always practical. This is because the distortion the floor framing system has experienced often has occurred over many years, and the wooden components that make up the floor system have warped and retain a “memory.”
Also, keep in mind that shallow foundation systems are designed to move. Therefore, some fluctuations should be expected. If annual shifts are not acceptable or become excessive, the only solution is to re-support the structure on deep piles.