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

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

In short: Osage is a thick, poorly drained clay soil on the flood plains of major streams in eastern Oklahoma. It is a Vertisol, the soil order defined by strong shrink-swell, with 40 to 65 percent smectitic clay and a water table that rises to 6 to 18 inches in winter and spring. Homes on Osage face clay movement, wet soil and floodplain exposure at the same time.

What is Osage soil?

Osage is an official USDA soil series classified as "Fine, smectitic, thermic Typic Epiaquerts" ¹. The "-ert" ending places it in the Vertisols, clay-rich soils that shrink and form deep, wide cracks when dry and expand when wet ³. That movement creates serious engineering problems ³.

The soil formed in thick clayey alluvium on flood plains along major streams, with slopes of 0 to 2 percent ¹. It occurs in southwestern Missouri, southeastern Kansas and eastern Oklahoma and is rated as extensive ¹. The type location is in Vernon County, Missouri, and the series was established in Bates County, Missouri, in 1908 ¹. Mean annual precipitation is about 39 inches (range 38-44) ¹.

In Oklahoma, Osage soils are mapped along streams in the Tulsa Metro, Northeast (Ozark Plateau and Grand Lake) and East-Central (Arkoma) regions, on Quaternary alluvium and terraces.

What is the typical soil profile?

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

• Clay: 40 to 65 percent in the subsoil; the control section averages 35 to 60 percent ¹.
• Mineralogy: smectitic ¹.
• Water table: apparent seasonal high water table at 6 to 18 inches, November through May in normal years ¹.
• Drainage: poorly drained; permeability very slow; saturated hydraulic conductivity low ¹.
• Redox features: present in all layers, reflecting wet conditions ¹.

What does Osage soil mean for foundations?

Strong shrink-swell

Slickensides, polished and grooved surfaces formed by repeated shrinking and swelling, are one of the diagnostic features of Vertisols ³. Osage has continuous, intersecting slickensides from about 13 to 60 inches ¹. A federal survey of expansive materials found that montmorillonite, a smectite clay, contributes to widespread expansive materials, notably in the Great Plains ⁴, and Osage is classed as smectitic ¹.

The USDA rates shrink-swell as linear extensibility, with 6 to 9 percent "high" and 9 percent or more "very high" ⁷. The rated value for each mapped unit is in Web Soil Survey ². Clayey soils heave as they gain water and settle as they dry, and uneven moisture change under a shallow foundation causes the damaging differential movement ⁶. Patterns to read about:

• Perimeter drying settlement (edge drop)
• Center heave
• Tree-root desiccation settlement

Wet soil

With the water table as high as 6 inches below the surface from November through May ¹, Osage soils are wet during the cool season. See groundwater and perched water, crawl space moisture and wood decay and lateral earth and hydrostatic pressure on walls.

Floodplain setting

Osage forms on flood plains ¹. The official flood hazard for an address is shown on FEMA's Flood Insurance Rate Maps, searchable by address in the Flood Map Service Center ⁵.

Related

• Clay mineralogy
• Shrink-swell and the active zone
• Soil series in the Tulsa metro
• Verdigris soil
• Soil series index