Concrete Foundations
Everyone knows that to build a house, one must start with the foundation. But do you ever stop to think about the type of foundation you’re walking around on? If you’re like most people, you probably take your home’s foundation for granted. That could be because you just aren’t familiar with what goes into building a foundation in the first place.
Foundations come in a myriad of shapes and sizes, and they can be built in several different ways. They can also be constructed from a variety of materials, including stone, brick, mortar, steel, and preservative-treated wood.The most common building material used for foundations today, however, is concrete.
There are four types of concrete foundations.
What is Concrete?
The word “concrete”comes from the Latin “concretus,” a compound word formed by joining the Latin “con” (together) with “crescere” (to grow). The substances used to make concrete are powdered cement, an aggregate (usually a gravel/sand combination), and water. The result is a soft substance that “grows together,” making it extremely hard and durable.
Concrete has a long and illustrious history. Materials with concrete-like properties were used in Syria and Jordan around 6,500 B.C., and the ancient Romans used concrete to build the Colosseum as well as the dome of the Pantheon.
Factors to Consider when Choosing a Foundation
Before deciding on a type of concrete foundation to be used, builders consider several factors, including the kind of structure to be built, the owner’s budget, and the building site. Also, soil, climate, and moisture all dictate what type of foundation can be built.
For example, homes in warmer climates tend toward having ashallow concrete slab foundation, whereas dwellings built in colder areas must have frost-resistant foundations, and they usually have basements. Residences in areas prone to flooding, such as coastlines, are often built on elevated foundations.
Tall buildings will need even deeper foundations using caissons, drilled shafts, and other stabilizing features that extend into thestronger rock below the surface.
Types of Concrete Foundations
Learning about concrete foundations can be confusing because of the many variables that go into construction. Some houses have simple foundation plans, while others require amore complex approach. Some buildings even combine two or more foundation types.
Foundation terminology can be complicated as well. A “post and pier” foundation is also known as “pier and beam.” Likewise, “raft” foundation is sometimes called a “mat.” But a foundation is usually one of four basic types: concrete slab, concrete block, T-shaped, and elevated.
Concrete Slab
A concrete slab foundation – also called slab-on-grade – consists of a single layer of concrete that is several inches thick and is even thicker along the edges. It usually rests on top of a layer of crushed gravel for drainage purposes. Metal rods and wire mesh are added to the slab for reinforcement.
Concrete slabs can be built upon a raised concrete perimeter supported by wider footing. Columns can be added above the slab to distribute weight from the building’s upper floors.
A floating slab is a type of concrete slab that is not anchored to the footings or supports under it. It is used for lighter structures such as garages.
A raft foundation (also known as a mat foundation) is a thick, reinforced concrete slab that extends throughout the entire structure to distribute the weight over a large area.
Concrete slab foundations are well-suited to warm, dry climates not prone to freezing or flooding.
Frost-protection is a feature that can be added to a concrete slab foundation to insulate it from freezing temperatures. An insulating material such as polystyrene can be placed under and next to the foundation walls when building the structure.
Concrete Block
Concrete block construction is used in colder climates where houses have basements. A hole to the depth of approximately 8 feet is excavated. Concrete beams are constructedandconcrete block foundation walls are built. Finally, a concrete floor is poured to complete the basement.
T-shaped foundations (sometimes referred to as spread footing) use footings placed below the frost line. Eachfooting is wider at its base, providing added stability and excellent weight distribution for load-bearing foundation walls.


Elevated foundations are necessary for locations prone to flooding and ground moisture. This type of construction also is referred to as “pier and beam” or “stem wall.” It utilizes concrete posts set deep into the ground to support the house’s actual foundation, which is raised about 18 inches off the ground.
Always consult a professional contractor or engineer as you are planning your structure. That way, you can be sure it meets all building codes and engineering standards.