What are foundation conditions like in Oklahoma City?

Reviewed by Preston · Updated 2026-11-11

In short: About 21% of Oklahoma City is mapped in soils rated high shrink-swell, 19% moderate and 33% low ¹. The city is so large that it holds very different ground: sandy soils over soft sandstone on the hills, clay soils formed from shale on the prairie, and clayey old terraces along the rivers. Only about 3% is poorly drained, so clay swelling and drought shrinkage, not perched water, drive most movement.

How much of Oklahoma City has expansive soil?

At about 607 square miles ², Oklahoma City crosses six county soil surveys (Oklahoma, Canadian, Cleveland, McClain, Grady and Pottawatomie) ¹. The citywide share of expansive soil is lower than in Moore or the Tulsa suburbs, but that average hides neighborhoods built almost entirely on clay next to others built on sandstone.

Which Oklahoma City soils matter most for houses?

• Stephenville, the most common classified soil in the city, is moderately deep and well drained, formed from Permian sandstone, with soft sandstone typically 20 to 40 inches down ³.
• Harrah is very deep to sandstone, well drained and formed in sandy and loamy colluvium on backslopes and foot slopes of low hills, on slopes of 3 to 45 percent ⁴.
• Darnell is shallow and sandy, with sandstone only 10 to 20 inches down ⁵. On these hills, fill, slopes and runoff matter more than clay swell.
• Renthin is deep, well drained and very slowly permeable, formed from clayey and silty Permian shale on prairie uplands ⁶. Soils like it carry the clay movement in the city.
• Kirkland sits on old stream terraces with a dense clay subsoil of 35 to 60 percent clay and slickensides ⁷. Norge, on the same old terraces, is less clayey ⁸.

Urban land, about 13% of the city, is ground mapped as covered by buildings and pavement rather than classified ¹.

How wet can Oklahoma City get?

Averages hide the swings that move clay. In May 2015, Oklahoma City received 19.48 inches of rain, its wettest month on record ⁹. Wet extremes after dry years are when heave and new cracks show up; see drought and wet years.

How deep is rock under Oklahoma City?

It depends on the bedrock unit. Public borings at the I-35/I-240 interchange in Hennessey shale hit bedrock between 2 and 41 feet ¹⁰¹¹¹², while borings in Garber sandstone at I-35 and Waterloo Road reached competent rock at 20.5 to 95 feet ¹³. See depth to rock in Tulsa and OKC.

Who can do foundation work in Oklahoma City?

Under Municipal Code Chapter 12-1, anyone contracting for a change, addition or improvement that needs a building permit must register as a building contractor, with a $100 annual registration fee, general liability insurance of at least $50,000 per occurrence, and workers' compensation coverage or an exemption form ¹⁴. See permits and licensing by city.

Which soils cover Oklahoma City?

ZIP codes in Oklahoma City

ZIP 73013, ZIP 73064, ZIP 73102, ZIP 73103, ZIP 73104, ZIP 73105, ZIP 73106, ZIP 73107, ZIP 73108, ZIP 73109, ZIP 73111, ZIP 73112, ZIP 73114, ZIP 73116, ZIP 73117, ZIP 73118, ZIP 73119, ZIP 73120, ZIP 73127, ZIP 73128, ZIP 73129, ZIP 73131, ZIP 73132, ZIP 73134, ZIP 73135, ZIP 73139, ZIP 73141, ZIP 73142, ZIP 73145, ZIP 73149, ZIP 73150, ZIP 73151, ZIP 73159, ZIP 73162, ZIP 73165, ZIP 73169, ZIP 73170, ZIP 73173, ZIP 73179

Looking for a foundation company near Oklahoma City?

Companies that serve Oklahoma City 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 Oklahoma City? 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.

Related

• OKC metro soils
• Hennessey shale
• Garber sandstone
• Shrink-swell and the active zone
• Compare Oklahoma cities