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

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

In short: Woodward is a moderately deep, well-drained silty soil of western Oklahoma that formed from soft, limy Permian sandstone and siltstone. It holds only 8 to 18 percent clay, and the soft rock usually sits 20 to 40 inches down. On Woodward land, foundation concerns tend to involve shallow soft rock, runoff on slopes and water management rather than clay swelling.

Where does Woodward soil occur?

The USDA Natural Resources Conservation Service (NRCS) keeps an Official Series Description (OSD) for each named soil. Woodward was established in Woodward County, Oklahoma, in 1944, and its type location is about a quarter mile south of Fort Supply ¹. It occurs across western Oklahoma, a few counties of southern Kansas and northwestern Texas, in the Central Rolling Red Plains (MLRA 78B and 78C), and its extent is large ¹.

Woodward forms on summits, shoulders and backslopes of interfluves and on side slopes of hills, ridges and escarpments, with slopes of 1 to 40 percent ¹. It is residuum from noncemented, calcareous, fine-grained Permian sandstone and siltstone, mainly the Marlow and Rush Springs formations of the Whitehorse Group, plus the Cloud Chief and Quartermaster formations ¹. For these rock units, see Western Permian Red Beds; Woodward occurs in the Northwest (Gypsum Hills) and Southwest regions of western Oklahoma ¹. Most Woodward land is grazed, with crops on gentler slopes ¹.

What are the key properties of Woodward soil?

The "Cd" layer at the base is soft sandstone or siltstone that breaks down to loamy material and has a root-restricting density ¹.

Associated soils include Quinlan, which is less than 20 inches to sandstone, along with Aspermont, Obaro and others ¹.

What do these properties mean for foundations?

Low clay content

NRCS rates shrink-swell by linear extensibility, with under 3 percent classed as low and over 3 percent able to damage buildings ³. Woodward's control section has only 8 to 18 percent clay ¹. The rated value for a map unit is in Web Soil Survey ². Western Oklahoma also has gypsum-bearing rock units, which the Oklahoma Geological Survey notes can dissolve and create sinkhole and collapse risks ⁵; see gypsum karst and sinkholes and the Permian gypsum units.

Shallow soft rock

On Woodward soils, soft sandstone or siltstone lies within 20 to 40 inches of the surface ¹. Because that rock is noncemented and breaks down to loam, it is not equivalent to hard bedrock ¹. See shale weathering and bearing strata.

Slopes, runoff and water

Runoff is low on 1 to 5 percent slopes and high on slopes steeper than 20 percent ¹. Loamy soils near foundations are where erosion, undermining and washout voids are evaluated. The ASCE homeowner guide recommends at least 3 inches of fall over the first 5 feet from the house, downspouts that discharge at least 3 feet out, and compacted clay rather than sandy soil for backfill against the foundation ⁴. Graded hillside pads may also involve fill consolidation settlement.

Related

• Quinlan soil
• Tivoli soil
• Northwest (Gypsum Hills)
• Surface drainage and grading
• Soil Series Index