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

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

In short: Hector is a shallow, stony soil that forms on sandstone ridgetops and steep mountainsides, with hard sandstone bedrock only 14 to 20 inches down. It is a sandy loam to loam, not a clay, and drains readily. For houses on Hector, the closeness of bedrock, steep slopes and control of runoff are the main soil factors.

Where does Hector soil occur?

The USDA Natural Resources Conservation Service (NRCS) Official Series Description (OSD) maps Hector in Arkansas, Alabama, Georgia, Kansas, Missouri, Oklahoma and Tennessee, probably on more than 800,000 acres 1. Its Major Land Resource Areas include 117 and 118 (Boston Mountains and Arkansas Valley), 116B (Ozark Border) and several Appalachian areas 1. The type location is in Washington County, Arkansas, and the series was established in Pope County, Arkansas 1.

Hector forms on nearly level to moderately steep ridgetops and steep to very steep mountainsides, on slopes of 2 to 60 percent 1. It weathered from sandstone bedrock, locally with some colluvium (material moved downslope) 1. For Oklahoma context, see the East-Central (Arkoma) and Southeast (Ouachitas and Red River) region pages and the rock units Pennsylvanian sandstones and Ouachita folded rocks.

What are Hector soil's key properties?

Property Hector (from the OSD) 1
Classification Loamy, siliceous, subactive, thermic Lithic Dystrudepts
Parent material Sandstone residuum, locally colluvium
Depth to bedrock 14-20 in (typical 15 in)
Drainage Well drained
Permeability Moderately rapid
Surface (A) Sandy loam, fine sandy loam or loam; 0-50% rock fragments
Subsoil (Bw) Sandy loam, fine sandy loam or loam; 0-35% rock fragments
Slopes 2-60%
Mean annual rainfall 45 in at the type location
Mean annual temperature 59.5°F at the type location

"Lithic" in the name refers to hard bedrock close to the surface, which the OSD puts at 14 to 20 inches 1. Hector is mostly low-grade cedar-hardwood forest, and cleared pasture is limited by droughtiness 1.

What does Hector soil mean for foundations?

Little clay

Shrink-swell movement comes from clay soils that swell when wet and shrink when dry 4. Hector's layers are sandy loam to loam with rock fragments 1. NRCS classes linear extensibility (LEP) under 3 percent as low 3; the LEP for each Hector map unit appears in Web Soil Survey 2.

Bedrock within 20 inches

Hard sandstone lies 14 to 20 inches below the surface 1. How shallow rock, ledges and weathered layers are evaluated as bearing material is covered in depth to rock from borings.

Steep slopes and runoff

The OSD describes runoff ranging from slow to rapid depending on slope, on ground as steep as 60 percent 1. Uneven moisture causes more foundation damage than uniform moisture, and the ASCE guide describes grading soil away from a foundation and discharging downspouts onto splash blocks away from the house to prevent erosion 4. Related topics: erosion, creeks and slopes and slope creep and lateral movement.

Fill on hillside lots

Where a building pad was cut into a slope or built up with fill, that fill is not part of the native profile described in the OSD 1; see fill consolidation settlement.

How do you check a specific lot?

Free, plain-English answers. It asks a few questions and walks you to the repair that fits.

Common questions

How deep is Hector soil?

Hector is shallow. The official description gives solum thickness and depth to sandstone bedrock of 14 to 20 inches, with bedrock at 15 inches in the typical profile.

Where is Hector soil found?

Hector is mapped in Oklahoma, Arkansas, Alabama, Georgia, Kansas, Missouri and Tennessee, including the Boston Mountains and Arkansas Valley. Its type location is in Washington County, Arkansas.

Is Hector soil expansive?

Hector is a sandy loam, fine sandy loam or loam with rock fragments, not a clay. The rated shrink-swell for a map unit is listed as linear extensibility in Web Soil Survey.

What grows on Hector soil?

Most Hector land is low-grade mixed cedar and hardwood forest of cedar, oak, elm, hickory and pine. Cleared areas used for pasture are limited by droughtiness.

Sources

  1. Official Series Description - HECTOR Series USDA Natural Resources Conservation Service
  2. Web Soil Survey - Home USDA Natural Resources Conservation Service
  3. Definition: Linear Extensibility Percent (LEP) UC Davis California Soil Resource Lab (from the NRCS National Soil Survey Handbook)
  4. Living With Shrink/Swell Soils: A Homeowners' Guide to Maintenance of Shallow Foundations American Society of Civil Engineers, Geo-Institute

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