What is Vernon soil and how does it affect Oklahoma foundations?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: Vernon is a red clay soil that formed in place from Permian red-bed claystone and sits on dense claystone 20 to 40 inches down. Its subsoil holds 40 to 60 percent clay, water barely soaks in, and it covers large areas of western Oklahoma and parts of the Oklahoma City area. Clay movement with moisture and the nature of the shallow claystone are the main foundation factors.

Where does Vernon soil occur?

The USDA Natural Resources Conservation Service (NRCS) keeps an Official Series Description (OSD) for each named soil. Vernon was established in Wilbarger County, Texas, in 1902, and its type location is about 12.5 miles south-southeast of Vernon, Texas ¹. The OSD places it in the Central Rolling Red Plains (MLRA 78B, 78C) and Rolling Limestone Prairie (MLRA 78A) of Texas, Kansas and Oklahoma, and calls it extensive ¹.

Vernon forms on hillslopes, pediments (gently sloping erosion surfaces at the foot of higher ground) and escarpments on dissected plains, with slopes of 1 to 45 percent, mostly 1 to 12 percent ¹. It is clayey residuum, meaning soil weathered in place, from noncemented Permian red-bed claystone ¹. In Oklahoma that ties it to the Western Permian Red Beds and the Hennessey Shale, across the Southwest, Northwest and OKC Metro. Most Vernon land is native rangeland ¹.

What are its key properties?

"Densic" bedrock is very dense but noncemented material; in Vernon it is red-bed claystone or dense clay, fractured at less than 4-inch spacing in its upper part ¹. Vernon has no clay-enriched "Bt" layer; its subsoil is a weakly developed "Bw" or lime-bearing "Bk" layer ¹.

Nearby soils include Tillman on flatter ground and Hollister on lower, flatter positions with smectitic clay ¹.

What do the properties mean for foundations?

Clay content

With 40 to 60 percent clay in the soil and in the claystone below it, Vernon is a clay soil top to bottom ¹. The OSD does not list a shrink-swell value or slickensides for Vernon ¹. NRCS rates shrink-swell by linear extensibility and notes that values above 3 percent can damage buildings and commonly need special design ³. The rated value for any map unit is in Web Soil Survey ². The Oklahoma Geological Survey notes that clay-rich shales and soils weathered from them can contain montmorillonite, which swells when wet ⁴. Lab tests such as plasticity index are explained on soil testing and lab values.

Shallow claystone

Footings and piers on Vernon lots meet dense claystone within 20 to 40 inches ¹. Because the claystone is noncemented and itself 40 to 60 percent clay, it is not equivalent to hard rock ¹. See shale weathering and bearing strata.

Runoff and uneven moisture

Very slow permeability and very high runoff mean rain mostly runs off, while water that does enter moves through the clay very slowly ¹. Localized moisture changes are more damaging than uniform ones, so the ASCE guide recommends even moisture on all sides, at least 3 inches of fall over the first 5 feet, and trees planted farther away than their mature height ⁵. Seasonal moisture change in expansive clays can reach 3 to 40 feet deep ⁶. Common patterns include perimeter drying settlement and perimeter wetting heave.

Related

• Tillman soil
• Hollister soil
• Shrink-swell and the active zone
• Soil series in the OKC metro
• Soil Series Index