Why Sioux Falls Driveways & Sidewalks Sink
Sioux Falls concrete does not sink because it was poured badly. It sinks because of where it sits: on soil that freezes 42 inches deep, thaws unevenly every spring, and washes out from under slabs with the snowmelt. Concrete Raising Sioux Falls wrote this guide because the cause decides the fix — and because no local company had explained it.
Minnehaha County's own building handbook (2021 IRC) sets the frost line at 42 inches minimum, with a winter design temperature of -11°F. That is the climate your driveway lives in. Here is what it does to concrete, and what lifting does about it.
Frost heave: the lift you do not want
Water in the soil freezes and expands, and the ground heaves upward — unevenly, because the soil is not uniform. A slab rides up on one side and not the other. When the thaw comes, the slab settles back, but not to the same place: the soil beneath it has shifted, compacted and, in places, washed away. Repeat that for a few winters and a level driveway becomes a tilted one. Frost heave is why settlement in Sioux Falls is worst in late March and April, when the frost is coming out of the ground.
Spring snowmelt: the washout
Sioux Falls gets its water all at once in spring: the snowpack melts, the ground is still frozen underneath, and the water has nowhere to go but across the surface and into every joint and crack. It carries fine soil out from under driveways, patios and sidewalks — the same fine soil the slab was resting on. A slab can look fine in February and drop an inch in April, and the cause is the water you watched run off your driveway. Roof runoff makes it worse: a downspout discharging at a slab edge concentrates the whole roof's meltwater on one spot.
Clay, glacial till, and the Big Sioux River valley
The soils under Sioux Falls are glacial till and clay — the kind that swells when wet and shrinks when dry, and that holds water against a slab instead of draining it away. The Big Sioux River valley adds its own drainage patterns, and the low ground near the river stays wettest longest. Clay is also why a dry summer can settle a slab just as surely as a wet spring: the soil shrinks, the support disappears, and the slab drops into the gap.
Settling fill: the new-subdivision problem
The fastest-growing parts of the metro — Tea, up 41% since 2020, and Harrisburg, up 52% — are built on fill: soil moved, graded and compacted to make lots out of prairie. Fill keeps compacting for years after the house is built, and the concrete on top of it follows it down. Driveways, sidewalks and garage floors on fresh fill are the first to sink, and they are also the easiest to lift — because the concrete is new and sound, and only the support underneath is missing.
What to do about it
First, lift the slab: fill the voids, restore the grade, seal the joints. Second, fix the water: point downspouts away from slabs, keep joints sealed, and make sure the ground slopes away from the house and the driveway. Third, time it right: book the assessment at the thaw, when the settlement is visible and the ground is ready to work. The cost guide has the prices; the contact page takes photos for a first estimate.
Questions
Why does my driveway sink every spring?
Because the frost heaves the soil in winter and the spring snowmelt washes it out from under the slab. The settlement shows worst in late March and April, when the frost comes out of the ground — and that is the best time to lift it.
Is Sioux Falls frost really 42 inches deep?
That is the figure in Minnehaha County's Residential Building Handbook (2021 IRC): frost line depth, 42 inches minimum. It is the code depth for footings — and the reason every slab in the county lives on ground that freezes and heaves.
Can anything stop my concrete from sinking again?
Lifting fills the voids and sealing the joints keeps water out — and water is the cause. Fixing drainage (downspouts, grading) protects the lift. Nothing makes a slab immune to frost, but a lifted, sealed slab on a filled base holds.