In the previous two sections of our "A Strong Foundation" episode of Blueprint for Home Building, you've found out about footings, how they're installed, who inspects them and how they're protected. But
The foundation is as important as any other element of your structure. It's what takes all of the loads from the roof to the walls to the floors, and it takes them and transfers them into your soil.
Three Types of Foundations
In building today there are basically three types of foundations:
- Basement — If you're in the North, you most likely have a basement. A basement can be thought of as a really extruded crawl space foundation. Basements are popular in the East and in many older areas because they do provide additional space for the family. When a basement is converted into a living space it's possibly the least expensive way to expand the home.
- Crawl Space — If you're in the middle portion of the country, due to the frost lines not being quite as deep, you probably have a crawl space. A crawl space — or raised foundation — is a common type that you'll find in home construction. This foundation gets its name due to the fact that it's built above the ground, allowing for just enough room to crawl underneath. There are stem walls on the perimeters, pierced in-between and then a girder system and floor joists on top of that. The foundation is high enough to that you have at least 2' under there to crawl around to take care of the mechanical systems of the house.
- Slab — If you're down in the South, you probably have a slab. A slab foundation is usually concrete poured directly onto the ground. You would dig the perimeter footings and then you would also remove enough of the soil and grade so that you pour the slab and the footings at the same time. You typically find this type of foundation in a tract-home environment where they're building a lot of houses and it's more of a similar situation each time. It's very efficient and it's a cost savings to do it this way. Also, the soil conditions may prevent you from putting in a basement. This type of foundation is also different from other foundations in that it uses concrete — not wood — to help support the weight of the home.
Note: There are always exceptions. There are basements in the South, for example.
Typically you'd choose your foundation type — either slab on grade, crawl space or basement — based on the local conditions and the local building tradition. In many areas of the West you will almost always see slab on grade because land is somewhat cheaper and you can build a larger home without using a basement.