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

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

In short: Apperson is a clay soil formed from Pennsylvanian limestone on the prairie uplands of north-central and northeastern Oklahoma. It is a Vertisol, meaning its smectite clay shrinks and swells enough to crack open and close with the seasons. It sits on hard limestone 40 to 60 inches down and stays wet through winter and spring, so both seasonal heave and settlement are common concerns.

What does the official description say?

The typical profile is in Osage County, about 1 mile north of Foraker ¹. Most Apperson land is native range, hay meadow or pasture, with some cropland ¹.

Reading the class name

• Fine, smectitic means the subsoil is clayey and dominated by smectite, the clay mineral family that swells most when wet; the smectitic class is stated in the USDA description ¹.
• Hapludert places it among the Vertisols, soils defined by shrink-swell clay, in a humid climate.
• Aquic means it is saturated for part of the year ¹.

What signs of shrink-swell are in the profile?

The USDA description reports cracks that open and close periodically, slickensides in the Btss and BCss horizons, and shiny pressure faces on the clay ¹. Slickensides are polished, grooved surfaces formed when clay masses shear past each other as they swell.

Soil scientists rate shrink-swell by linear extensibility, the percent change in a soil's length from moist to dry. Under 3 percent is low and 9 percent or more is very high ². The Apperson description does not give a number, so the map-unit value in the USDA Web Soil Survey is the place to confirm it for a lot.

What is the limestone underneath like?

Apperson forms on Pennsylvanian limestone ¹. In northeastern Oklahoma, limestone units such as the Oologah are described as blue cherty limestone with bands of black shale, about 80 to 145 feet thick ⁴. See Pennsylvanian limestones.

What does Apperson soil mean for foundations?

• Seasonal heave and settlement. Smectite clay over rock swells when wet and shrinks when dry, and uneven moisture causes more damage than uniform change ¹³. On this soil, slab edges can drop in late summer and rise in wet spells. See perimeter drying settlement, perimeter wetting heave and center heave.
• Winter and spring wetness. Perched saturation from December through April and slow permeability ¹ can keep crawl spaces damp and add pressure on below-grade walls. See crawl space moisture and lateral earth and hydrostatic pressure.
• Trees. Tree roots draw water from clay soils and are a recognized cause of local drying under foundations ³. See tree-root desiccation settlement.
• Moisture practices. The ASCE guide recommends grading at least 3 inches of fall in the first 5 feet, discharging downspouts at least 3 feet out, watering evenly and planting trees farther from the house than their mature height ³.

Related

• Tulsa metro
• Northeast (Ozark Plateau and Grand Lake)
• Pennsylvanian limestones
• Cracks that open and close seasonally
• Soil series in the Tulsa metro