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

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

In short: Konawa is a deep, well-drained soil formed in old sandy and loamy stream deposits on low terraces in Oklahoma's Cross Timbers. It has a sandy surface over a sandy clay loam subsoil with 18 to 30 percent clay, and bedrock lies deeper than 80 inches. Its loamy texture means foundation issues on Konawa more often trace to water, drainage and fill than to clay swelling.

What is Konawa soil?

Konawa is an official USDA soil series classified as "Fine-loamy, mixed, active, thermic Ultic Haplustalfs" ¹. "Fine-loamy" refers to the texture of its subsoil, which is fine sandy loam or sandy clay loam ¹.

The soil formed in loamy and sandy alluvium of Pleistocene (Ice Age) age on the treads and risers of low stream terraces ¹. Slopes range from 0 to 20 percent ¹. It occurs in the North Cross Timbers (MLRA 84A) of Oklahoma, Kansas and Texas and is rated as extensive ¹. The type location is in Payne County, about 8 miles west of Perkins, and the series was first established in Pottawatomie County in 1965 ¹. Konawa soils were formerly included in the Dougherty series ¹.

In Oklahoma, Konawa areas fall in parts of the OKC Metro and East-Central (Arkoma) regions, on Quaternary alluvium and terraces.

What does a Konawa soil profile look like?

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

• Drainage: well drained ¹.
• Permeability: moderate; saturated hydraulic conductivity moderately high ¹.
• Runoff: negligible on 0-1 percent slopes, low on 1-5 percent, medium on 5-20 percent ¹.
• Depth to bedrock: more than 80 inches ¹.
• Climate: mean annual precipitation about 36 inches (range 31-43) ¹.
• Native vegetation: post oak, blackjack oak and hickory with a grass understory ¹.

What does Konawa soil mean for foundations?

Shrink-swell

Shrink-swell soils change volume as moisture changes, and the USDA measures this as linear extensibility: under 3 percent is low and 3 to 6 percent is moderate ³. Konawa's subsoil clay content is 18 to 30 percent ¹; compare higher-clay central Oklahoma claypan soils such as Kirkland. The rated linear extensibility for each mapped unit is available in Web Soil Survey ².

Water, leaks and fill

On loamy and sandy soils, the more common questions involve how water moves and whether the soil under a footing has been disturbed:

• Moderate permeability ¹ means water from roofs, irrigation and plumbing leaks soaks in and moves through the soil. The ASCE Geo-Institute guide lists roof runoff, poor grading, irrigation and plumbing leaks as the key moisture sources to control around shallow foundations ⁴.
• That guide suggests discharging downspouts at least 3 feet from the foundation and keeping sprinkler heads at least 5 feet away ⁴.
• Where a sloping terrace lot was leveled with fill, see fill consolidation settlement and fill soils and lot history.
• For how running water can carry sandy soil out from under slabs and footings, see erosion, undermining and washout voids.

How do you confirm the soil at a property?

Web Soil Survey shows the mapped soil units for an area, covering more than 95 percent of U.S. counties, and can generate custom soil reports ². Because soil maps are general, a boring or test pit is the way to confirm the layers under a specific house; see soil testing and lab values.

Related

• Dougherty soil
• Pulaski soil
• Surface drainage and grading
• Plumbing leaks under slab
• Soil series index