By: Brian Hale 6/27/2011
When estimating for a remodel or finish out in an already standing building, there are many factors to consider regarding existing conditions. One of these factors is the foundation of the building structure.
Not all foundations are created equal. The many different soil types and rock formations in the DFW Metroplex require different types of foundation systems. In most cases a new floor plan requires new plumbing fixture locations or electrical chases. In this situation a concrete slab will have to be saw-cut, demolished, or cored and eventually poured back or patched.
Whenever possible it is important to acquire the original building foundation and framing structural drawings which should indicate which type of foundation system the building has. Sometimes, it is not cost effective to put a certain plumbing fixture or piece of equipment at a certain location because of a post-tension cable or a structural beam present directly below. The structural drawings will allow us to overlay the new space with the existing structure. This gives us an opportunity to see any potential issues before construction that can be dealt with a quick design change. If these problems are not detected early, the project timeline will be stagnated and will likely require costly corrective measures.
The cost and method of foundation removal and replacement will vary depending on the foundation type. Some foundations may appear to be a standard slab-on-grade, but will actually have a crawl space (whether accessible or inaccessible) beneath them. A common type of this foundation is designed to self-support itself with heavy amounts of steel and/or post tensioned cables. We typically refer to this foundation as a Structural Slab. In this case an x-ray or sonogram of the foundation may be required if the foundation plans can’t be found. In this case, instead of saw-cutting, the concrete will most likely have to be cored at each fixture location and the piping will be routed inside the crawl space rather than in soil. If a standard slab-on-grade is present, the slab will have to be removed, drilled and doweled into, and poured back. The subgrade will also have to be compacted, a weather barrier placed, and a reinforcing inspection will have to be performed by the local municipality prior to slab-pour back.
All work that occurs in and beneath the slab is performed at the beginning of your project. It is important that the project gets started with a strong, smooth running start to build momentum for a strong finish.