If you live in Des Moines and have a sunken driveway, uneven sidewalk, or settled patio, you're dealing with a problem that's remarkably common in Iowa — and one that has specific, identifiable causes. Understanding why concrete sinks helps you choose the right fix and avoid the same problem recurring.
1. Iowa's Clay Soil Compresses and Erodes
The number one cause of concrete settlement across the Des Moines metro is the soil itself. Iowa's heavy clay subsoil compresses under load, expands when wet, and shrinks when dry. Every freeze-thaw cycle pushes and pulls the ground beneath your concrete. Over years and decades, this constant movement gradually destroys the compacted subbase that holds concrete in place.
Clay also erodes. When water moves through or under clay soil — from rain, drainage, or even sprinkler systems — it carries clay particles with it, slowly hollowing out the ground beneath concrete slabs. The slab has nowhere to go but down.
2. Poor Compaction During Original Installation
Concrete is only as stable as the subbase it sits on. When subbase material isn't properly compacted before concrete is poured — which happens frequently on new construction projects under time pressure — the soil continues to settle for years after the pour. This is why so many Iowa homeowners notice their driveway or sidewalk starting to sink within 5–10 years of a new home being built.
Common in fast-growth suburbs: Ankeny, Waukee, and Bondurant have seen the most concrete lifting calls from newer homes in the last 5 years — directly tied to rushed subbase preparation during the construction boom.
3. Water Erosion Under the Slab
Water is the primary long-term enemy of concrete stability. Sources include: downspouts discharging near the slab, improper yard grade that sends surface water under the concrete edge, underground drainage that's failed and allows water to pool below, and irrigation systems with heads positioned too close to concrete. Each of these slowly washes away subbase material, creating voids. When voids get large enough, the slab above them cracks and drops.
4. Tree Roots
Tree roots do damage in two ways. Active roots grow under concrete and push it up (heaving), creating a raised trip hazard. Dead or dying roots decompose, leaving voids that cause the concrete above to sink. Johnston, Urbandale, and Clive — Des Moines suburbs with the most mature tree coverage — see the highest rate of root-related concrete problems.
Important: If a tree root is actively growing under your concrete, lifting will be a temporary fix. The root will continue to grow and eventually cause the same problem again. We'll advise honestly when root removal or panel replacement is more appropriate than lifting.
5. Iowa's Freeze-Thaw Cycle
Des Moines averages 50+ freeze-thaw cycles per year. Each cycle, any water present in the soil beneath concrete freezes, expands (by about 9%), and then thaws and contracts. This repeated expansion and contraction gradually loosens compacted subbase material, widens existing voids, and shifts concrete slabs from their original positions. Over decades, this alone is sufficient to cause significant settlement even on properly installed concrete.
Does Sinking Concrete Mean I Need Replacement?
Not usually. If the concrete slab itself is structurally sound — not crumbling, not broken into small pieces, not severely cracked through — it can almost always be lifted back to its original position. Lifting costs 50–75% less than replacement and is done in hours rather than weeks. The key question is whether the concrete itself is salvageable, which an on-site assessment answers in minutes.
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Bottom Line
Iowa concrete sinks because of clay soil movement, poor original compaction, water erosion, tree roots, and freeze-thaw cycles — often in combination. Understanding the cause is the first step to choosing the right fix. In most cases, concrete lifting addresses the root cause (filling the void) and the symptom (raising the slab) simultaneously, at a fraction of replacement cost.