The Three Main Types of Foundations

General Article

The foundation is the first part of a home that is constructed. It creates a base for the rest of a home’s parts. If a foundation is not good, the rest of the house will have problems. Because there are options for choosing a foundation type, builders and home owners have an important decision to make. Any decision concerning a foundation should be made while keeping in mind the cost, market demand, soil composition, and weather conditions of the area.

There are three main types of foundations: full-height basement, crawlspace, and slab-on-grade. All of these foundations do a more than adequate job of supporting a house.

Full-Height Basement

Full-height basement foundations provide an accessible space between the soil and the bottom of the first floor of a home. This space can be finished to provide extra space for a family or left unfinished and used primarily for storage. This type of foundation provides more head room for individuals than a crawlspace will allow.

This foundation type is typical in an area with a colder climate where the foundation needs to be below the frost level. A foundation needs to be below the frost level to prevent it from cracking.

Crawlspace

A crawlspace foundation creates an accessible space with limited headroom between the soil and the bottom of the first floor. This type of foundation is predominantly used in areas with heavy clay content in the soil.

The crawlspace foundation does not provide a new room for a family to use but it does allow for ample storage.

Slab-on-Grade

Slab-on-grade foundations are the least complicated of the foundations. It is just a structural concrete slab poured directly on the dirt. There is no accessible space between the foundation and the dirt because the foundation sits on the dirt.

This type of foundation is popular in areas that have a high water table. The water table is the depth to which an individual must dig before he or she can find water.

All of these foundations are generally constructed from concrete. There are options to concrete though. The two main ones are Concrete Masonry Units (CMUs) and Insulated Concrete Forms (ICFs).

Concrete Masonry Units (CMUs) are hollow, concrete blocks similar to cinder blocks. The hollow portions are filled with concrete from top to bottom to hold the blocks together and to hold the wall together.

Insulated Concrete Forms (ICFs) are rigid foam insulation forms into which concrete is poured. The insulation forms are made of a mold, hardware, and any necessary bracing a wall or foundation could use.

After the concrete hardens in the form, the outside, the inside, or both forms are removed. This type of construction is common in areas that have building codes which require insulated foundations. The biggest benefit of this type of foundation is that the homeowner or builder can immediately finish the basement without adding studs.