Foundation repair contractors in Dallas County

Dallas County is not one soil. The bedrock exposed at the surface is all late Cretaceous, but it arrives in three north-trending belts: "the Eagle Ford Shale in the western part of the county, the Austin Chalk through the central part, and the Taylor Marl in the eastern part," with the harder chalk determining most of the relief and forming the White Rock escarpment in the southwest (Soil Survey of Dallas County). A house on the west side and a house on the east side are sitting on different parent rock, even though both are called Blackland Prairie.

What each belt weathers into

The Eagle Ford Shale "weathers to an unstable, highly plastic clay that is very susceptible to slumping and sliding," producing Vertel and Heiden clays that carry "the same high plasticity and shrink-swell potential as their parent material." The Taylor Marl in the east yields "the black, waxy Houston Black clay," also rated highly susceptible to slumping and sliding. Austin silty clay is the common soil over the chalk (same survey).

At county scale the survey is blunt about the consequence: the soils are clayey with "a high content of the clay mineral montmorillonite," and shrink-swell "creates such movement and pressure that walls and foundations will crack unless they have been adequately designed and carefully installed." The series it names as most susceptible are Branyon, Burleson, Ferris, Heiden, Houston Black, Ovan, Trinity and Vertel (same survey). Houston Black is the county's most extensive series; several of these clays are given plasticity indices of 28 to 42 in the adjoining county's engineering tables (Soil Survey of Tarrant County).

The exception worth knowing: Pleistocene terraces cover more than 30 percent of the county, and sandy or loamy Silstid and Silawa soils formed on them (Soil Survey of Dallas County).

Development scale

By the time the survey was published, about 46 percent of the county was already in urban uses, and the 1970 census counted 1,327,321 residents (same survey). Much of the built area predates current slab design practice.

Permit rules, engineer-letter requirements and watering schedules are set by each city, not the county. Those are covered on the individual city pages.