House Plan Foundations Explained

by Dan Sater II March 07, 2019 4 min read

What type of foundation do you need? Are you familiar with the terminology used to describe foundation types? Do you understand the need for or the benefits of the different types of foundations? Hopefully we can answer some of those questions here. Learning a little bit more about foundations is always a good thing.

It all starts with the foundation. The stability of the home is rooted, if you will, in the foundation. However a foundation is not always simply a structural element to a home. It is possible that their function can follow their form.

Every house plan comes with a default foundation type - a foundation the house was originally designed to rest upon. However this is not always the last word. Many plans offer different options for foundation types. In fact, if you do not see a foundation option, or the type of foundation you wish is not listed in the options, please contact us. Many times we are able to modify a plan to get you the foundation you need.

Understanding Foundations

It is best to have a basic grasp of the most popular types of foundations. While there are many different varieties and combinations of foundations, this list will cover the most widely used types.

Stem-Wall Slab Foundation

There are three parts to the Stem-Wall Slab. There is the footer, the stem wall, and the slab. The concrete stem-walls are set on top of the footers. They rise above the ground level to provide a raised platform for the slab to sit upon. The exterior walls of the house are then built on the stem walls.

Monolithic Slab Foundations

Monolithic slabs are poured concrete that are typically 4 to 6 inches deep. They have thickened perimeter edges. They will also have thicker areas within the slab for load bearing walls. The soil underneath must be level and properly compacted. Monolithic slabs must be at least 6 inches above grade.

Crawl Space Foundation

Much like the Stem-wall slab foundation, the crawl space foundation starts with a footer. Then a stem wall is built upon that. Typically a crawl space is between 24 and 48 inches above grade. A wood platform is built on top of the stem walls which support the house. Additional pilings under the house may be added for additional support.

Full Basement Foundation

Most people will be familiar with the idea of a full basement. It also has a footer as well as a wall. They support the load of the house above. A floor of poured cement is added, typically 4 inches thick. As with the crawl space, additional piling support may be added.

Walkout Basement Foundation

This is the same as a full basement. However, the back wall of the foundation is not underground. Typically this is used on lots with a steep slope. These types of basements can add lots of utility while at the same time taking advantage of the lot's views.

Piling or Island Basement Foundation

This type of foundation is most commonly seen in coastal locations. It consists of either wood or concrete pilings that have been driven into the ground. Then a platform is built on top of the pilings. The load of the house is carried by the platform and transferred down the pilings to the ground. The ground can either be left uncovered, or it can be covered in gravel, paver stones, or even a concrete slab. This area under the home should not be used for living spaces but they can make great garages, work shops and storage spaces.

Picking the Right Foundation

The type of foundation you will need depends on your lot conditions, as well as the local building codes. A full basement, if possible and allowed, is a great way to add extra living space. It is a great value as the space doesn't need to be finished at the time of construction.

The use of a monolithic or stem-wall slab foundation will depend on the lot as well. A very flat level lot can get away with a simple monolithic slab. But if the lot has a slight slope, a stem-wall slab would be the best choice. Either one is very energy efficient, more so than any other type of foundation.

The crawl space foundation can save a little money as it is simpler to build. It also works on sloped lots, and it gives a little protection from flooding. It can also be a bit easier when it comes to working on plumbing and electrical as it is easier to access than on a slab foundation.

The Island basement has a most specific roll. That would be to protect from water damage due to storms and floods. However it does offer features that might be beneficial to a home that will not face floods or storm surge. Drive under parking is a great space saver. You get the features of a full garage without the need for the extra room in the lot. The elevated living area can also be great for views. 

When it comes down to picking the right foundation, it is really up to you and your lot. But now you know the basics. Combined with the knowledge of your lot's physical layout and your local building codes, you will be ready to pick the right foundation for your new home.


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