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

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

In short: Kirkland is a very deep, well-drained soil on old stream terraces in central Oklahoma, with a dense clay subsoil that holds 35 to 60 percent clay. Its subsoil shows slickensides, which form when clay swells and shrinks over and over. Homes on Kirkland soil are exposed to seasonal shrink-swell movement.

What is Kirkland soil?

Kirkland is an official USDA soil series classified as "Fine, mixed, superactive, thermic Udertic Paleustolls" ¹. The word "Udertic" marks a vertic intergrade, a soil that trends toward the Vertisols, the order of clay soils defined by shrink-swell behavior ³. Vertisols crack deeply when dry and swell when wet, and that movement creates serious engineering problems ⁴.

The soil formed in clayey sediments over Permian shale on paleoterraces (old, high stream terraces) in the Central Rolling Red Prairies ¹. Slopes are 0 to 3 percent ¹. The series occurs in central Oklahoma and south-central Kansas and is rated as extensive; its type location is in Logan County, about 4 miles south and 8 miles west of Guthrie ¹. Mean annual precipitation is about 32 inches ¹.

In Oklahoma this places Kirkland in the OKC Metro and North-Central (Red Prairies and Wheat Belt) regions, over red-bed shale units such as the Hennessey Shale and Wellington Formation.

What does a Kirkland soil profile look like?

Source for the table: ¹. Other properties from the official description ¹:

• Slickensides: the Btss and Btkss layers have prominent intersecting slickensides ¹.
• Permeability: slow; saturated hydraulic conductivity is low ¹.
• Bedrock: a paralithic contact (weakly cemented siltstone) at about 82 inches in the typical pedon ¹. Paralithic material is partially weathered or weakly consolidated bedrock ³.
• Drainage: well drained, medium runoff ¹.

What does Kirkland soil mean for foundations?

Seasonal shrink-swell

Clay soils swell (heave) as they gain water and shrink (settle) as they dry ⁵. Uniform changes in soil moisture are less damaging than localized changes ⁵. Slickensides are polished, grooved surfaces formed by this repeated shrinking and swelling ⁴, so their presence in Kirkland's subsoil ¹ is a field sign of a soil that moves.

The standard soil-survey measure of this behavior is linear extensibility. On a percent basis, 6 to 9 percent is "high" and 9 percent or more is "very high" ⁶. For vertic subgroups like Kirkland, soil taxonomy uses a total linear extensibility of 6 cm or more in the upper 100 cm as a key criterion ³. The value for the mapped unit at a specific address is listed in Web Soil Survey ².

Common patterns on soils like this include:

• Perimeter drying settlement (edge drop) during droughts.
• Perimeter wetting heave (edge lift) after wet periods.
• Center heave as moisture builds under a slab.
• Tree-root desiccation settlement near large trees.

Moisture management factors

The ASCE Geo-Institute homeowner guide lists moisture sources to manage on shrink-swell soils, including rainfall and downspouts, poor drainage, sprinklers and overwatering, drought, trees, plumbing leaks and shallow seepage ⁵. It suggests discharging downspouts at least 3 feet from the foundation and grading at least 3 inches of fall in 5 feet ⁵.

Statewide soil moisture is tracked by the Oklahoma Mesonet, which measures it at 5, 25, 60 and 75 cm depths with a network of more than 110 stations covering all 77 counties ⁷.

Related

• Shrink-swell and the active zone
• Renfrow soil
• Norge soil
• Soil series in the OKC metro
• Heave vs settlement
• Drought and wet cycles