Slab-on-grade
Slab homes and additions across the county settle for one reason more than any other: the soil under one part of the slab gave way while the rest held.
The early signs are rarely dramatic. A tile line cracks across a hallway. A kitchen island sits noticeably lower than the run of cabinets. Baseboard opens a gap along one wall and stays tight along the opposite one. By the time a slab crack is wide enough to catch a fingernail, the section it separates has usually dropped somewhere between a half inch and two inches. Because you cannot see the foundation itself, the symptoms arrive indirectly, through finishes and door frames, and homeowners often spend a year blaming the flooring installer before anyone takes a level to the room.
The dominant soil across this county is Drummer silty clay loam, a very deep, poorly drained soil formed in loess over stratified glacial drift. The type location for the Drummer series is on the University of Illinois south farm, which is to say the textbook example of this soil is in Champaign County. Poorly drained silty clay does two things a slab does not like: it swells when it takes on water and it consolidates when it is drained, especially where fill was placed and not compacted properly during construction. Add a slab that spans that variable support with relatively little reinforcement and you get differential movement rather than uniform settlement, which is what cracks concrete.
Where the slab has dropped and needs support, underpinning is the answer. Push piers are steel tubes driven hydraulically through the soft material using the weight of the house itself as the reaction load, advancing until they meet refusal on a firm stratum. Helical piers are screwed in with a torque motor, and the installation torque gives a direct reading of soil capacity as they go. On heavier structures push piers work well because there is enough load to drive them. On lighter structures, additions, porches, and garage slabs, there may not be enough weight to develop the driving force, and helicals are the better tool. Anyone who uses one system for every condition is selling what they own rather than what the site needs.
Once piers are in, you have a choice. Stabilizing means holding the structure where it currently sits so it stops moving. Lifting means attempting to bring the settled section back toward its original elevation. Lifting sounds obviously better and often is not. Finishes, plumbing, tile and drywall have all adjusted to the settled position over years, and pulling the structure back can open cracks that had closed and break connections that had settled into equilibrium. A good contractor will tell you honestly how much recovery is realistic and what is likely to crack on the way up. Getting most of the way back and stopping is frequently the right call.
For an exterior pier installation the crew excavates a working pit at each pier location down to the footing, which means the landscaping along that elevation comes out. Brackets are attached to the footing, the piers are advanced, and load is transferred. Interior work through the slab means cutting and removing sections of floor, which is dusty and loud, and the flooring in that area will need replacing afterward. A modest job of six to eight piers on one corner is often a few days. A full perimeter is considerably longer. Ask specifically whether the quote includes backfill, compaction and restoring the grade, because a pier job that leaves loose fill against your wall has set up the next problem.
Not every slab problem needs piers. Where the concrete is still at grade but the soil beneath it has consolidated away, you have a void, and the slab is spanning it until it cracks. Injecting grout or polyurethane foam through small holes fills that void and restores continuous bearing. This is a much smaller job than underpinning and is the right answer surprisingly often, particularly in garages and on additions built over poorly compacted trench backfill. The way to distinguish the two conditions is elevation readings plus, in some cases, sounding the slab for hollow response.
Three things, mostly. How many piers, which follows from how much of the perimeter has moved. How deep each pier has to go before it reaches competent bearing, which on variable glacial drift can differ significantly across a single house. And access, because a pier location behind a deck, under a bay window, or against a neighbouring property line takes far longer than one in open lawn. Beware any quote given by phone or from photographs alone. Nobody can price depth without probing for it, and depth is the largest single variable in the number.
Structural work of this kind will generally require a permit. Inside the City of Champaign, permits run through the Building Safety Division under the Fire Department, the city adopted the 2021 International Codes in January 2024, and applications have gone through an online portal since the start of 2025. Contractors have to be registered with the city to pull one. Urbana runs its own building department, and each village administers its own. Confirm who is pulling the permit before work starts, and keep the final inspection sign-off with your house records. It is the document that answers a future buyer's inspector.
Not all slab settlement comes from the soil drying or consolidating on its own. A supply line or drain leak under the slab saturates a localised area of subgrade, and on silty clay that either softens bearing or washes fines away, producing a void. The tell is settlement that does not match the pattern you would expect from grading or fill, particularly a low spot centred under a bathroom or kitchen rather than at a corner. An unexplained rise in the water bill, a warm spot on the floor over a hot line, or the sound of running water with everything shut off all point the same direction. Underpinning over an active leak is money spent on a problem that will continue, so it is worth ruling out first.
If you map slab problems across a typical Champaign County house, they cluster at additions, attached garages and enclosed porches rather than under the original structure. There are two reasons. Those elements are frequently built on backfill or on shallower footings than the main house, and they carry much less weight, so they respond more to soil movement rather than being held down by their own load. They are also often unheated, which means the ground beneath them freezes more deeply than it does under the conditioned part of the house. When a homeowner describes a crack running along the line where an addition meets the original wall, that is usually two structures moving at different rates rather than one structure failing.
Before you hire anyone in Illinois: there is no statewide general contractor license in this state. Contractor registration is handled by individual municipalities, and the City of Champaign requires contractors to be registered with the city to pull a permit. Ask who is pulling the permit, ask for written proof of liability coverage and workers' compensation, and get the scope in writing.
Tell us which rooms feel off-level and how long it has been that way. That detail shapes the first visit. Call (217) 882-0544 or send the form, and an independent foundation contractor working in Champaign County will follow up with you directly.
Call and describe it. It costs nothing to find out whether you are looking at a maintenance item or a structural one.