Older housing stock
Champaign and Urbana have a deep supply of pre-war housing, and a fair amount of it is carried on interior piers and wood girders rather than a continuous footing.
It is almost never the whole structure at once. A single interior pier settles, or the wood column sitting on it crushes and shortens, and the girder above it sags a half inch. The floor joists follow. Upstairs you get a soft spot in the middle of a room and a door frame that racks out of square. On the older stock around campus and in the near-north Urbana neighborhoods, the original piers are frequently brick or dry-stacked block sitting on a shallow pad that was never carried below frost. They held for eighty years because they were carrying modest loads on undisturbed soil, and they start moving when something changes: a bathroom added upstairs, a wall removed, or water finding its way under the crawl space.
It helps to understand that these were not mistakes by the standards of the time. Interior piers inside a crawl space are shielded from direct frost exposure, so a shallow pad often performed adequately for decades. What changed is moisture. When drainage around the house degrades and the crawl space soil becomes seasonally saturated, that soil loses bearing capacity and becomes frost-susceptible in a way dry soil is not. Silty clay is the worst offender because its fine particle size holds a great deal of water, and water is the fuel for frost heave. The pier did not fail because it was badly built. It failed because the ground under it stopped behaving the way it did in 1925.
The other half of the problem is decay. When a crawl space has no vapor barrier over exposed clay, ground moisture moves up through the soil and into the framing all season. Sill plates, beam ends and joist ends at the perimeter take the worst of it, because that is where wood meets masonry and where condensation collects. A beam that has lost section to rot will keep deflecting no matter how many times the pier under it is shimmed. Probing suspect timber with an awl is the standard field test: sound wood resists, decayed wood takes the point with almost no pressure.
New footings poured below the local frost depth, new steel or treated columns set on them, sistered or replaced framing where the wood has gone soft, and the floor jacked back in controlled increments. Footing size matters as much as depth, because a small pad on soft silty clay will simply punch down again. On weak soil the answer is often a larger pad, or helical piers where a poured footing cannot reach adequate bearing. Confirm the footing depth being proposed and confirm it against what the local building department requires, rather than accepting a number by habit.
Lifting a settled floor too fast is how you crack the plaster you were trying to save. Wood framing, lath, drywall joints and door casings have all crept into the settled shape over years, and they need time to redistribute stress. Competent crews raise in small increments over days or weeks, often an eighth of an inch at a time, checking as they go. Any contractor who talks about raising a full inch in a single day is telling you something about their process. Expect some cracking regardless. The goal is controlled, repairable cracking rather than a torn ceiling.
Homeowners are frequently unprepared for the noise. Houses being lifted pop, tick and groan as fasteners release and framing shifts. Doors that closed fine may bind for a few days and then free up as the lift completes. Interior trim gaps open and close. None of that is necessarily a problem, but it is unsettling if nobody warned you. Ask the contractor to walk you through what to expect at each stage, and agree in advance who is responsible for the cosmetic repairs afterward, because that is the single most common source of dispute on this kind of job.
Access is the dominant factor. A crawl space with thirty-six inches of headroom and a decent hatch is a very different job from one with eighteen inches, a tight opening, and ductwork in the way. Beyond that: how many piers and columns, how much framing has to be replaced rather than sistered, whether the crawl space has to be pumped and dried before anyone can work, and whether the mechanical systems running through the space need to be temporarily moved. Get the quote to break out structural work from any moisture control, so you can see what you are actually buying.
If the crawl space is open and the crew is already in there, this is the moment to deal with the ground cover, the perimeter drainage and any plumbing that has been leaking. Doing it later means paying twice for access. A sealed ground cover over exposed soil is inexpensive relative to the structural work and it directly addresses what caused the failure. Fixing the exterior grading at the same time completes the loop. Repair the structure, remove the water, and the repair holds. Repair the structure alone and you are on a clock.
When joists or a beam have lost strength, there are two approaches. Sistering means fastening new material alongside the damaged member so the pair carries the load together, which is faster, cheaper and entirely appropriate where the original still has meaningful section left. Replacement means removing the damaged member entirely, which is the honest answer when rot has consumed the bearing end or when insect damage runs the length of the piece. The failure mode to watch for is sistering onto wood that has nothing left to contribute, which produces a repair that looks substantial and performs like half of one. Ask which is being proposed for each member and why, and ask how the new material bears at each end, because a sistered joist that stops short of the support is carrying nothing.
Homeowners often start this conversation because a room is cold rather than because a floor is sloped, and in an older pier-and-beam house the two are related. Fibreglass batts in a damp crawl space absorb moisture, sag out of the joist bays and stop insulating long before anyone notices, and ductwork running through that space loses conditioned air through joints that were never sealed. If the framing is being repaired anyway, the insulation and duct sealing in the same bays is the cheapest it will ever be to address, because the access has already been paid for. Get it quoted as a separate line so you can see the cost, but get it quoted.
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.
Note where the floor dips and whether any doors have started sticking, then send it over. 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.