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

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

In short: Eram is a clayey soil of eastern Oklahoma that sits on weathered Pennsylvanian shale 20 to 40 inches down. Its subsoil holds 35 to 55 percent clay, is extremely hard when dry, and lies under a seasonal water table 1 to 2 feet deep in winter and spring. Wet-season saturation, dry-season shrinkage and shallow weathered shale are the main traits that affect foundations.

Where does Eram soil occur?

The USDA Natural Resources Conservation Service (NRCS) Official Series Description (OSD) maps Eram in Oklahoma, Kansas and Missouri, in Major Land Resource Areas 76, 84A, 112, 118B and 119 ¹. It is moderately extensive ¹. The type location is about 5 miles northeast of Beggs in Okmulgee County at 775 feet elevation, and the series was established in Okfuskee County in 1942 ¹.

Eram forms on interfluves and hillslopes, including ridges and side slopes of hills, on slopes of 1 to 20 percent ¹. Its parent material is Pennsylvanian shale with thin sandstone layers ¹. Okmulgee and Okfuskee counties lie in the East-Central (Arkoma) region, south of the Tulsa metro.

What are its key properties?

"Consistence" describes how hard or firm a soil feels; "extremely hard when dry" is a sign of a dense clay. Eram is mainly rangeland of tall grass prairie, with some cropland and tame pasture ¹.

What do the properties mean for foundations?

Clay that wets and dries

Clay soils swell when they gain water and shrink when they dry, and uneven moisture causes more damage than uniform moisture ⁴. Eram combines 35 to 55 percent clay with a water table that rises to 1 to 2 feet in winter and spring ¹. NRCS classes linear extensibility (LEP) under 3 percent as low, 3 to 6 percent moderate, 6 to 9 percent high and 9 percent or more very high ³; the LEP for each Eram map unit appears in Web Soil Survey ². See perimeter wetting heave and perimeter drying settlement.

Shallow weathered shale

The bedrock layer (Cr) is weathered shale or compacted clay beds, reached at 20 to 40 inches ¹. Weathered shale is not the same as hard rock, a distinction covered in shale weathering and bearing strata. In Oklahoma steel push pier records, piers typically reached 8 to 16 feet, with a median near 12 feet in Tulsa ⁵. Below 31 inches, Eram's saturated hydraulic conductivity drops as low as 0.01 micrometers per second ¹, meaning water moves through the lower layers very slowly.

Water management

The ASCE homeowner guide describes grading soil away from the foundation, discharging downspouts away from the house and having leaks isolated and repaired ⁴. Eram's seasonal water table already sits 1 to 2 feet down in winter and spring ¹. See surface drainage and grading and groundwater and perched water.

How do you check a specific lot?

• Look up the map unit, depth to bedrock, water table and LEP in Web Soil Survey ².
• Watch for stair-step brick cracks, sticking doors and sloping floors, and track cracks over time ⁴.

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