What are foundation conditions like in Stillwater, Oklahoma?

Reviewed by Preston · Updated 2026-11-11

In short: About 33% of Stillwater is mapped in soils rated high shrink-swell ¹, led by Renfrow clay formed from Permian shale. Sandstone hills and small-creek floodplains break up the clay, so conditions change across town.

How much of Stillwater has expansive soil?

Stillwater covers about 30 square miles ², in the Payne County soil survey ¹.

Which Stillwater soils matter most for houses?

• Renfrow, about 18% of the city, formed from clayey Permian shale on low hills; below about 13 inches it is clay, with seasonal cracks, slickensides and a high linear extensibility ³.
• Norge is deep and well drained on old upland terraces, less clayey than Renfrow ⁴.
• Grainola is moderately deep, formed from Permian shale on low hills ⁵; Mulhall is very deep, formed in colluvium over silty Permian shale on backslopes and footslopes ⁶.
• Coyle is moderately deep and well drained, formed from Permian sandstone on crests and side slopes of low hills ⁷.
• Easpur and Pulaski are floodplain soils of small streams ⁸⁹; Pulaski floods occasionally to frequently for very brief periods between March and October ⁹.

What does Stillwater require for footing depth?

The City of Stillwater's adopted construction standards list a frost depth of 18 inches, based on an air freezing index of 500 ¹⁰. Footings must reach below frost depth, but on Renfrow clay the seasonal moisture swing can reach deeper than that, which is why the active zone matters more than frost for foundation movement. See permits and frost depth by city.

Which soils cover Stillwater?

Looking for a foundation company near Stillwater?

Companies that serve Stillwater can appear on the company map in the Homeowner Hub. Paid listings there are marked Sponsored; the library and the AI guide don't rank or recommend any of them.

Buying or selling a house in Stillwater? Realtors who serve the area can be on the same map, also marked Sponsored, and for realtors covers the seller disclosure form, inspections and the sale timeline. Seeing cracks at home? Start with for homeowners.

How were these numbers measured?

We overlaid the city's current limits from the Census Bureau ² on the USDA soil survey's map units ¹ and added up the area of each soil. Where a map unit is a mix of soils, its area was split by the percentages the survey lists for its major soils, so the shares above leave out minor inclusions and do not add to 100%. A soil counts as high, moderate or low shrink-swell by the linear extensibility of its most expansive layer, the survey's measure of how much a soil changes length between wet and dry (6% or more is rated high). Water table, bedrock and flooding come from the survey's map-unit summaries: the shallowest water table in any month, the shallowest bedrock, and the most common flooding frequency. Bedrock here includes soft, weathered sandstone and shale that a pier can push through, so it is not the depth where piers stop. These are mapped averages for the whole city, not a test of any one lot. Fill, grading and the soil actually under a house can differ, which is why a site visit or soil boring still decides a repair.

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