A crawl space offers room beneath the floor for ductwork.
Your home's foundation serves as the structural base that supports the rest of the house, but foundations are not alike. A slab foundation is just that – a solid slab that separates the frame of your home from the soil. A crawl space foundation is like a mini basement minus a concrete floor and with walls too short to allow the average person to stand up. Choosing the right foundation depends on site conditions, local building codes, your budget and the features you'd like included in your new home.
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Slab foundations are popular in regions where a high water table makes pouring a crawl space or basement unfeasible. In addition, a slab is indicated in a patio-type home that requires handicapped access, such as wheelchair ramps and ground level entrances.
Crawl Space Foundations
A crawl space foundation is desirable on a sloping site, when a basement isn't feasible. But like a basement, a crawl space may not be appropriate with a high water table because constant moisture in the crawl space may be detrimental to the floor joists and the subfloor. Crawl space specifications also depend upon the frost line where you live. In colder regions, a crawl space requires taller walls in order for the footings to be below the frost line. In areas where the frost line is deeper than 6 or 7 feet below grade, consider putting in a full basement, which you can use for additional storage or living space.
Plumbing and Mechanical Considerations
One of the biggest differences between a slab foundation and a crawl space is the installation and maintenance of the plumbing and mechanical elements. In a crawl space, the contractor will make provisions for the drains and then the plumber will install the pipes beneath the floor and attach the drains later. With a slab, however, all drains must be in place before the contractor pours the slab. Likewise, in a crawl space, wiring, water supply pipes and ductwork are run beneath the subfloor. The contractor will have to install these elements in the walls and in the ceiling if you choose a slab foundation.
Generally, it's less expensive to pour a slab foundation because it requires less excavating and less labor to form the slab for pouring. It may also require less concrete. However, if you should have trouble down the road with the drainage system, repairing it can be expensive. Before choosing a foundation call your local building authority. In some communities, you must install a specific type of foundation.