What soils cause foundation problems in southwest Oklahoma?

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

In short: Southwest Oklahoma has some of the state's most strongly shrink-swell soils. Deep clays such as Hollister and Tillman crack more than 30 inches deep in dry periods ¹², and Foard, another cracking clay, carries a sodium-rich subsoil ³. With only about 22 to 32 inches of rain a year in much of the region ¹³, long droughts dry these clays deeply, and wetting from rain, irrigation or leaks makes them swell.

Cities covered: Lawton, Altus, Chickasha, Anadarko and Frederick.

What is the climate like?

USDA descriptions for the region's clay soils list mean annual precipitation of about 22 to 32 inches and mean annual temperatures of about 57 to 65 °F ¹²³. Toward Chickasha on the eastern side, soils list about 35 to 41 inches ⁵. Statewide, Oklahoma's climate shifts from humid subtropical in the east to semi-arid in the west ⁷. See drought and wet cycles.

What is the ground made of?

Most of the region lies in the Central Rolling Red Plains land resource area, where soils formed in clayey alluvium and Permian red beds ¹³⁴.

Deep-cracking clays

• Hollister: very deep, well drained clays with very slow permeability, formed in Pleistocene clay alluvium over Permian sediments. USDA classifies Hollister as a smectitic Vertisol (Typic Haplustert): slickensides begin about 8 to 20 inches deep, and cracks deeper than 30 inches stay open 150 or more days in most years ¹.
• Tillman: very deep clays from Permian red-bed clay and claystone, with slow permeability, cracks more than 48 inches deep and a COLE (coefficient of linear extensibility, a shrink-swell measure) above 0.06 in the upper 40 inches. The series was established in Tillman County ².
• Foard: clays from old granitic outwash of the Wichita Mountains over Permian clays, with very slow permeability, vertic cracking and slickensides, and a natric (sodium-rich) subsoil within about 22 to 66 inches, with exchangeable sodium of about 15 to 25 percent in its lower layers. Type location is in Cotton County ³.

Expansive clay changes volume as its water content changes. Shrinkage cracks do not close up perfectly on rewetting, and alternating rainfall and drought produce seasonal cycles of swelling and shrinkage ⁸.

Red-bed claystone and sandstone soils

• Vernon: moderately deep clays over dense red-bed claystone at 20 to 40 inches, with very slow permeability; lower layers can hold some gypsum, soluble salts and sodium ⁴.
• Chickasha: well drained loamy soils from Permian sandstone with weakly cemented sandstone at 40 to 60 inches; the series was established in Washita County ⁵.

See western Permian red beds and Wichita granite and granite wash.

Gypsum and karst

The Oklahoma Geological Survey reports gypsum and shallow salt deposits in many areas of western Oklahoma, and limestone and dolomite karst in the Limestone Hills north of the Wichita Mountains ⁶.

Which soils are most common?

What are the common foundation problems?

• Perimeter drying settlement and tree-root desiccation settlement on deep-cracking clays.
• Center heave and leak-related heave when water collects under slabs.
• Soil pulled away from the foundation and wide surface cracks in summer.

Statewide research estimated active zone depths of about 0.5 to 4 meters, depending on soil and climate ⁷. Cracks recorded deeper than 30 to 48 inches in Hollister and Tillman ¹² show that seasonal drying reaches well below the surface in these soils.

Related

• Shrink-Swell and Active Zone
• Clay Mineralogy
• Western Permian Red Beds
• Northwest (Gypsum Hills)
• South-Central (Arbuckles & Texoma)