USDA soil data · Des Moines
The ground under Des Moines swells and shrinks enough to crack a foundation
We pulled USDA soil-survey ratings for Des Moines and scored two things that wreck foundations and basements: how much of the ground is expansive clay that moves with the seasons, and how much of it drains slowly and holds water against the wall.
17% of the ground sampled in Des Moines is high shrink-swell clay.
What this means if you own a home in Des Moines
Your home is sitting on ground that changes size. Expansive clay swells when it soaks up water and shrinks back as it dries out, and it does that every wet season and every drought. That movement is the number-one cause of foundation damage in the country, and it shows up as stair-step cracks in brick, doors and windows that start to stick, gaps opening at the corners of the house, and sloping floors.
None of this is covered by a standard homeowners policy, earth movement and seepage are both excluded, so the cost of catching it early or letting it spread is entirely on you. The fixes are known and routine: proper grading and gutters to keep water off the soil, foundation drainage and waterproofing, and for active movement, piering or wall stabilization. The earlier a pro looks at it, the cheaper it stays.
The ground under Des Moines, from the survey
USDA maps Des Moines as mostly Nodaway soil (Nodaway, occasionally flooded-Urban land complex, 0 to 2 percent slopes). Here is how the 12 rated sample points break down.
2 of 12 rated points are high shrink-swell, peaking at 7.5% linear extensibility. Above 6% is where clay moves enough to threaten a foundation.
6 of 12 rated points drain slowly (hydrologic groups C and D), so water tends to pool and press against foundation walls rather than soak away.
Read the low numbers carefully
This rates the soil, the top meter or so of ground. Where the expansive material is deep claystone bedrock below the soil, like the Pierre Shale under the Colorado Front Range, the soil-level number reads low even though the ground moves plenty. So a low clay score here is not proof of stable ground, only that the shallow soil is not the problem.
These are 17 sample points across Des Moines, not your specific lot. Soil varies block to block. Treat this as the odds for the area, and get your own ground looked at before you decide.
Where this comes from
Source is USDA NRCS SSURGO, the national soil survey. We sampled the dominant soil component on a grid across Des Moines and read its linear extensibility (LEP, the shrink-swell measure) and hydrologic drainage group. A point counts as high shrink-swell at LEP of 6% or more in the top 100cm. The dominant soil series held across 200% of sampled points.
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Des Moines soil and foundations: FAQ
Is Des Moines built on expansive clay?+
Yes, in part. 17% of the ground USDA sampled across Des Moines rates as high shrink-swell clay, and the worst point measured 7.5% linear extensibility. That clay swells when it gets wet and shrinks as it dries, and the movement cracks foundations from below.
Why is my foundation cracking in Des Moines?+
The two usual culprits are the ground itself. Expansive clay heaves and drops a foundation as it swells and shrinks with the seasons, which shows up as stair-step cracks in brick, sticking doors, and gaps at the corners. Slow-draining soil holds water against the wall until it finds a crack. Des Moines shows moderate clay movement and moderate drainage risk, so both are worth an inspection.
Does homeowners insurance cover foundation damage from soil in Des Moines?+
Almost never. Standard homeowners policies exclude damage from earth movement and settling, which is exactly what expansive clay causes. That means prevention and early repair are on you, which is why catching it before it spreads matters.