If you want to build your house on a foundation with better curb appeal and resale potential than a monolithic concrete slab, you have three choices. You can go all out and treat yourself to a full basement, save some expense and build over a crawl space, or choose a raised concrete slab. The biggest factor that's likely to influence your decision is money, but it shouldn't be the only one.
1. A Place for Everything
The one unquestionable advantage of basements is the reason that they were invented in the first place: They add usable space to your home. At the very least, they provide a place for items like your furnace, water heater, electrical boxes and other household items. A basement that's properly designed and finished can even add a significant amount of real, practical living space. While some crawl spaces may provide storage space, their use is usually limited, and a house built on a raised slab has no usable under-floor space.
2. Can't Get There from Here
Sometimes the most convenient place to run the plumbing, heating duct work and wiring that serves the first floor of your house is directly under the floor itself. However, in a house with a raised slab foundation, plumbing and wiring could have been run under the slab before it was poured. That means access for repairs or changes after construction can be difficult and costly. A crawl space offers room to run services under the floor, but the access is still limited and more difficult than it would be in a full basement.
3. Easy on the Feet
Concrete is hard, and when your house is built on a slab, the ground floor is made of concrete. The wooden joists and sub flooring that support the ground floor on crawl-space and full-basement foundations are more flexible and, in the long run, easier on your feet. Crawl spaces allow for a more forgiving floor, but they present their own challenges; if not properly maintained, ground water, run-off and pests could get into them, creating a damp, unpleasant and potentially structurally problematic space. Basements can be damp, too, but if they're adequately waterproofed and ventilated, they're much more inviting than a dark, moldy pest-infested crawl space.
4. Time is Money, and a Basement Requires Both
The major disadvantage of a basement lies in the fact that it is, essentially, a big hole in the ground. It takes time and money to dig that hole and pour the basement walls. The time needed to excavate, build forms, pour concrete and allow the concrete to cure can add a week or more to your home's construction schedule, not to mention thousands of dollars in labor and materials. Depending on the slope of the ground, crawl spaces, in comparison, do not require as much excavation and concrete and therefore take significantly less time to build. Likewise, raised slab foundations often require little excavation and are usually the fastest and cheapest type of foundation to build.
5. Location, Location, Location
Depending on where you live, a basement might not even be an option for you. In locations with unstable soil, high groundwater levels or tough bedrock near the surface of the ground, excavating for a basement could be impractical, if not specifically against local building codes. However, considerations such as where your frost line is may end up making a basement the cheaper and smarter option. Whatever foundation you decide on, though, check with your local codes to make sure you are compliant.