Foundation Types of Texas Homes

Foundation Types of Texas Homes

Foundation Types

One of the biggest concerns for home buyers in Texas is a foundation issue. Here, we provide you with some basic information about house foundations.

There are three foundation types most commonly used for single family homes in the United States: basement foundation, slab foundation, and pier and beam foundation.

Foundation type is mainly determined by local climate and soil conditions, house design, and construction budget. 

As shown in the expansive soil map above, most houses in Texas are built on expansive clay soils. Expansive clay soils are a source of foundation issue because they shrink and swell depending on their moisture content. To prevent foundation damages from expansive and collapsible soils, houses need to be equipped with proper drainage system and landscape irrigation system around the perimeter to keep uniform and constant moisture level in the clay soils all year round.

 

Basement foundation: This type of foundation is most commonly found in areas with cold winters where concrete footings of foundation are required to be five or more feet deep from the ground level, so they will not be moved by water or freezing ground in the winter. Because soil pressure increases with depth, a foundation wall below the grade must be strong enough. The Foundation wall can be constructed of poured concrete, cinder block, concrete block, brick, or wood.

Pro: It can provide underground spaces for extra living rooms as well as locations for storage, furnace, and water heaters.

Con: Basement flooding can be caused by heavy rain when the house has the following issues: foundation cracks, poor drainage system around the house (negative grade, clogged gutters or downspouts), lack or malfunctioning of sump pump, sanitary or storm sewer backup, and so on. Because the basement is vulnerable to water intrusion, the basement will become humid and favorable to growing mold.

As shown in the frost line map above, basements are not common in Texas where the frost line is less than a foot depth. Most common type of house foundation in Texas is either slab foundation or pier and beam foundation.

Slab foundation: Slab foundation is very common in the southern United States where the frost depth is very shallow. Slab foundation is a concrete pad poured on the ground with the use of rebar reinforcement. It is also called slab on grade foundation.

Pro: The installation of slab foundation is simpler and quicker compared to other types of foundations. It is also less expensive and provides better protection against termite infestation.

Con: Since it can be built directly on the ground, there is no crawl space or basement below the slab. Water supply and drainage pipes are embedded in the concrete and can be damaged in the event of foundation settlements and cracks.

There are several types of slab on grade foundations: floating, supported, monolithic, and post-tension slabs.

Foundation Type for Expansive Soils: Post-Tension Slab
 Post-tension slab  is a kind of monolithic slab that utilizes cables within slab instead of rebar reinforcement, which are tensioned after the slab cures. Post tensioning compresses the concrete and holds the entire slab together as one piece. This can help reduce foundation problems for the house if there is any underlying settlement or expansion of the soil.

Pier and beam foundation: A pier and beam foundation is one of the oldest foundation types used in residential construction. It is not built directly on the ground but elevated at least 18 inches above, creating a crawl space surrounded by short foundation walls. The house rests on girder beams that are supported by piers.

Pro: The space between the first floor and the ground forms a crawl space which provides convenient access to plumbing pipes and electrical wiring.

Con: Uninsulated water pipes in the crawl space can freeze in extremely cold winter weather. If crawl spaces are not ventilated properly, excessive moisture can build up, causing problems of mold and rotting floor structures. Rodents and other small pests can intrude into the broken vents.