Before you can even start thinking about designing or building a house, you must determine what kind of foundation is necessary. The decision point usually lies between a slab foundation or a pier and grade beam foundation. Each comes with its own set of challenges. For information on identifying problems in your foundation check out our homeowners guide.
Factors in Determining Foundation
While there are many factors to take into consideration, there is one that holds the most weight. The main factor to consider is soil.
Rocky or sandy soil is excellent to build a foundation on. Water does not easily influence or damage the structure. This is because there is nothing to hold onto the moisture.
Clay soil, however, can be found in many areas in north Texas. As rainwater, sprinklers, or other water sources come into contact with the clay soil under your foundation it drastically expands. This expansion lifts the structure. As the soil dries, it contracts causing your house to sink again. This constant movement can destroy a home if the foundation is not chosen carefully.
If you live in an incredibly rocky or sandy area, the choice is easy: slab foundation. This is because there will be little movement. A slab is easier to maintain and cheaper to construct.
However, if you are considering building your home on expansive soil, a pier and grade beam foundation is fundamental. Because the home is raised off of the ground, the soil will have less of an impact on the foundation.
Pier and Grade Beam Components
A pier and beam home consists of a few basic parts, namely the piers, beams, joists, footing, vents, and sill plate. It is also common to have a concrete footing or a grade beam along the perimeter.
As you can tell in the picture above, the weight of the structure is distributed among multiple block piers. These piers are pushed into the earth using a hydraulic jack. Each pier will be pressed into the ground until it hits bedrock or a point of refusal, typically between 7 and 20 feet.
Piers are placed in horizontal or vertical rows under the structure. Each row is about 10 feet apart. Piers in each row are 5 feet apart.
After piers have been placed, beams installed on each row of piers.
Joists are installed perpendicular to the beams in order to support the flooring of the structure.
Grade Beams
Now that the interior of the structure has been covered, it is important to mention the perimeter.
There are two approaches to supporting the perimeter of the home, a concrete footing or a grade beam. A grade beam differs from a concrete wall footing in the method the weight is distributed. A grade beam will distribute the weight into pilings, while a wall footing distributes the weight into the soil beneath it. While each has its benefits, today we will be talking about grade beams.
A grade beam, or grade beam footing, is a reinforced concrete beam that is used to distribute the weight of a load-bearing wall evenly between piles, caissons, or directly on the soil. Grade beams are at least 8 inches wide. The depth is equal to the distance between each support.
These are typically installed on steep slopes, where the soil is active and a deep foundation is necessary.
For more information on foundation construction and components please refer to our blog, as we will be posting more content daily.