A foundation plan is a drawing or illustration that shows the footings, piers, or structural underpinnings needed to support the building. It provides all the information needed to prepare a strong base in which to build your home. Several factors come into play when determining which foundation to use. Depending on where you build, only certain types of foundations can be used. For instance, areas near the ocean are not ideal for basement foundations. Another governing factor is the make-up of your house site plan. The grade of the land or slope of the lot dictates what foundation type would be best to use. Other things that may affect your foundation choice include soil conditions and building codes.
There are typically three foundation types in which a home is built on. The least complex of the three is called a slab or monolithic foundation. The second type is known as a crawlspace which has pier support. The third foundation type is known as a basement which is generally beneath ground. Each one has its own need and purpose when it comes to building your home. Listed below are the different foundations found in a set of house blueprints.
Slab Foundation Plan
A slab is essentially a continuous pour of concrete that is monolithic in nature. The foundation is designed with footings on the perimeter of the slab as well as within the floor to support the weight of the building. (Best for lots that are relatively flat.)
Crawl Space Foundation Plan
A crawlspace is to be raised at least eighteen (18) inches above the finished grade to the bottom of the floor joist for the main floor. These joist are supported by girders (support beams) which are supported by piers which are supported by concrete pad footings. The piers are strategically spaced apart in order to carry girders that will ultimately carry the load that is distributed across the floor joist from the weight of the home. The perimeter of a crawl space foundation is usually a CMU (concrete masonry unit) wall or poured concrete wall supported by a continuous footing. (Ideal for level lots or home sites with moderate slopes.)
Basement Foundation Plan
A basement can be described as a mix of a slab and crawlspace with taller walls. Like the crawlspace, the perimeter walls are poured concrete or CMU, only they are 9 feet or more in height. The floor is a monolithic pour as in the slab foundation. (Ideal for hillside lots and land with significant sloping. Can also be used on moderately flat lots for fully submerged basements)
In the case of either foundation, the page may also consist of sectional details of the foundation to illustrate further clarity if space permits. If not, they are shown on one of several architectural detail sheets. These details show the foundation as if it was cut through a section to view how it is put together. You also see this type of cut-through for the foundation on the “building section” sheet as well.