Home Building Basics: Deciding on a Foundation

Neighborhood construction with house foundation in the foreground and partially finished house in the background.

If you're constructing a house or adding on a room, you will encounter the question of what foundation to build. Depending on where you live in the country, your home will likely be built on one of three types of foundations: slab, crawl space or full basement. Each has advantages and disadvantages and, generally related to climate, are common in different areas of the country. Here's a quick overview of each type of home foundation and some of their pros and cons.

Slab Foundations

If you're constructing a house or adding on a room, you will encounter the quest

The Pros: Time and Initial Cost

Common in warmer climates where frost isn't an issue, slab foundations are popular with both builders and home owners since they minimize the amount of time needed to build a home. Without the necessity of digging a large hole for a crawl space or full basement, homes built on slabs can be constructed much quicker and at significantly less cost than homes built on other types of foundations.

Slabs provide a solid, level surface for floors so homes built on slabs don't often have problems with creaking floors or doors that won't open and close as a house settles over time.

The Cons: Moisture, Pests, and Future Costs

On the downside, slab foundations in general are prone to moisture and pest intrusion, since they are literally set on the ground.

However, perhaps the largest potential problem with a slab foundation is that since plumbing and wiring is run through the slab, repairs are difficult and expensive if anything breaks.

Crawl Space Foundations

The Pros: Moisture and Pest Prevention

Built on raised walls set on concrete footings, a home with a crawl space is raised slightly above the ground (2 to 3 feet). This prevents moisture and pest intrusion while providing an open and accessible yet enclosed space to run heating ducts, plumbing and wiring.

The Cons: Cost and Stairs

Some downsides to crawl space foundations include the cost to dig the shallow foundation along with the time needed to pour the footings and build the perimeter wall. Also, since the home is up above ground level, you need stairs to get into the house so accessibility can be an issue for some.

Full Basement Foundations

Common in warmer climates where frost isn't an issue, slab foundations are popul

The Pros: Extra Space

Common in colder areas of the country where the ground freezes in winter, a full basement is built in a hole dug 6 to 8 feet into the ground, below the frost line, to provide a stable foundation. Similar to crawlspace construction, the foundation is built on a set of concrete footings around an external perimeter wall above ground level and a concrete slab floor.

Full basements provide space for the household utilities along with the head space that allows for building full rooms below grade. (Building basement rooms is the least expensive floor space you can build in a home since the walls are already constructed).

The Cons: Time and Cost

The downsides to a full basement are similar to those of a crawl space foundation since over time the foundation will settle, floors will creak and doors may stick.

However, perhaps the largest downside to a full basement foundation is the time and cost associated with building it -- digging the hole and building the perimeter walls.