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

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

In short: Durant is a very deep clay soil of south-central Oklahoma formed from Cretaceous shale and claystone. Its subsoil holds 40 to 60 percent smectitic clay, and in dry periods it cracks more than 1 cm wide and 30 inches deep. Those traits mark Durant as a shrink-swell soil, so seasonal foundation movement is the central concern for houses built on it.

Where does Durant soil occur?

The USDA Natural Resources Conservation Service (NRCS) Official Series Description (OSD) places Durant in south-central Oklahoma, in Major Land Resource Area 85, the Grand Prairie of Oklahoma ¹. It is of moderate extent, and its type location is in Bryan County about 4 miles west and 1 mile north of Albany ¹.

Durant forms on flat to slightly convex summits, shoulders and backslopes of broad ridges, on slopes of 0 to 6 percent ¹. It weathered from clayey Cretaceous shale and claystone ¹. That places it in the South-Central (Arbuckles and Texoma) region, near the Southeast (Ouachitas and Red River).

What are its key properties?

"Udertic" means the soil is an intergrade toward the Vertisols, the soil order defined by shrink-swell clay. "Smectitic" means smectite is the dominant clay mineral. Durant is used for cotton, small grains, grain sorghum, tame pasture and range ¹.

Why does Durant soil move?

Vertic behavior

Vertisols are clay-rich soils that shrink as they dry and swell as they rewet, forming deep, wide cracks that open and close, and this shrink-swell action causes serious engineering problems including damage to structures ⁵. Durant does not fully meet the Vertisol criteria, but its OSD records cracks more than 1 cm wide and 30 inches deep in dry periods, with the moisture control section dry in some part for about 90 to 135 days a year ¹.

What that does to a house

Clay soils swell (heave) when they gain moisture and shrink (settle) when they dry, moving shallow foundations up and down ⁴. Uneven changes, such as a dry edge beside a wet interior, cause more damage than uniform ones ⁴. Common patterns include:

• Perimeter drying settlement in drought.
• Perimeter wetting heave after wet spells.
• Center heave as moisture builds under a slab.
• Tree-root desiccation settlement near large trees.

Warning signs include stair-step cracks in brick, sticking doors and windows, sloping floors and slab cracks 1/16 inch or wider ⁴; see cracks that open and close seasonally.

Measuring shrink-swell

NRCS rates shrink-swell by linear extensibility percent (LEP), the change in length of soil between moist and oven-dry: under 3 percent low, 3 to 6 percent moderate, 6 to 9 percent high and 9 percent or more very high ³. The LEP for each Durant map unit is published in Web Soil Survey ².

What are the practical points for a Durant lot?

• Look up the map unit and LEP in Web Soil Survey ².
• Keep soil moisture next to and under the foundation as uniform as practical ⁴.
• Plant trees farther from the house than their mature height; deep root barriers can help where trees are already close ⁴.
• Repair leaks promptly and keep sprinklers at least 5 feet from the foundation ⁴.

Related

• Shrink-Swell and Active Zone
• Clay Mineralogy
• Root Barriers and Moisture Control
• Bernow soil
• Soil Series Index