How does slab repair lift a house?

Supports are installed beneath the perimeter grade beam and driven down until they reach material capable of carrying load. A bracket then transfers some of the structure's weight onto each support. Because those supports sit on stable material rather than on soil that shrinks and swells, they provide a fixed reference — and hydraulic pressure applied against them can raise the slab section in controlled increments toward its intended elevation.

What is a grade beam?

The thickened, reinforced edge of a slab foundation, running around the perimeter and sometimes along interior load lines. It is deeper than the general slab thickness and carries concentrated load from the walls above. It is also where perimeter underpinning connects, because it is the part of the foundation stiff enough to take a bracket and transfer load into a pier.

Is slab repair permanent?

Underpinning driven to refusal is designed as a long-term solution, and the supports themselves do not degrade in normal conditions. What determines whether the outcome holds is whether the cause was addressed. An active under-slab plumbing leak, uncorrected drainage concentrating water at one corner, or supports that stopped on an obstruction rather than competent material can all allow movement to continue. The warranty document states what coverage applies and for how long.

Does the whole slab get lifted?

Usually not. Repair is targeted at the area where the elevation survey shows movement, which is commonly one section of the perimeter rather than the entire footprint. Lifting an entire slab uniformly would achieve very little, since uniform movement causes little damage. The point is correcting differential movement, so the work goes where the differential is.

Can slab repair be done on a post-tensioned slab?

Yes, and the same underpinning principles apply. The important difference is that post-tensioned slabs contain stressed steel tendons, so any operation involving cutting or coring requires those tendons to be located first. The evaluation should identify the slab type, and any proposal involving penetration should say how tendon location is handled.

What Is Slab Foundation Repair? How It Works

A plain explanation of what slab foundation repair involves, written for homeowners meeting the subject for the first time.

What a slab foundation is

A slab-on-grade foundation is a single reinforced concrete pour that sits directly on prepared ground. There is no crawlspace and no basement — the floor of the house is the top of the foundation.

Around the perimeter, and often along interior load-bearing lines, the concrete is thickened into what is called a grade beam. That thickened section is deeper and more heavily reinforced than the general slab, because it carries concentrated load from the walls above and spreads it into the ground.

Most Fort Worth homes built from the 1950s onward use this construction. Newer subdivisions increasingly use post-tensioned slabs, where steel tendons are stressed after the concrete cures rather than relying on conventional reinforcing steel alone. That distinction matters for any work involving cutting into the slab.

What goes wrong

The slab itself is rarely the problem. What moves is the ground beneath it.

Expansive clay soils change volume with moisture content — swelling when wet, shrinking when dry. When that happens evenly around a house, very little changes. When one area dries faster than another, or one area stays saturated, the support beneath the foundation becomes uneven and the slab responds.

Downward movement where support has been lost is settlement. Upward movement where soil has swelled is heave. They look similar from inside the house and they require different responses, which is why the heave versus settlement guide exists as a separate piece.

Steel pier section positioned in an excavated hole next to a concrete slab grade beam

Underpinning, in plain terms

Remedial underpinning transfers part of the building’s load past the soil that moves, onto material that does not.

The upper zone of soil — where moisture changes with the seasons — is sometimes called the active zone. Below it sits material that stays more consistent: dense clay, limestone, or another firm layer, depending on the site.

A support is driven down from an excavation at the grade beam until it reaches that material. A bracket is fixed to the underside of the beam, and the load path now runs from the wall, through the beam, into the bracket, down the support, and into stable ground.

Driving to refusal

The phrase you will see in every proposal is “driven to refusal”. It means the support is advanced until the resistance it encounters reaches a defined threshold — the point at which it can no longer be meaningfully advanced against the available reaction.

That threshold is a measured condition, not a target depth. Two supports on the same house can reach refusal at noticeably different depths because what is beneath them differs. A proposal stating a single fixed depth for every location is describing an assumption rather than the ground.

It is also worth knowing about premature refusal: a support can stop on an obstruction — old concrete, rubble fill, a rock fragment — and register resistance without having reached a genuine bearing layer. Installation records showing depth and pressure at each location are how that gets identified.

Bracket bolted beneath a grade beam transferring building load onto an installed pier

What a repair actually involves

Stage	What happens
Evaluation	Foundation type confirmed, relative elevations recorded, observations and site conditions documented
Scope	Method, number of supports and their locations, inclusions, exclusions, schedule, warranty
Permitting	Where required, application and inspection arrangements confirmed
Excavation	Access opened at each support location around the perimeter
Installation	Supports driven to refusal, depth and pressure recorded at each
Load transfer	Brackets fixed, load taken onto the supports
Lift	Where elevation recovery is part of the scope, staged adjustment with readings between stages
Restoration	Backfill, grade reinstatement, and whatever else the scope includes
Handover	Installation records, post-repair elevation documentation, warranty terms

The two systems used in residential work here are pressed concrete piling and driven steel piers. Both are driven; they differ in profile, reach, and cost. The repair methods page covers how the choice is made.

What repair does not do

It does not repair the cosmetic damage the movement caused. Some cracks close during a lift, some partially close, and some need patching or repointing afterwards. Those are separate line items.

It does not address an active plumbing leak, a drainage problem, or a moisture source. If one of those is the cause, underpinning without fixing it leaves the cause running.

And it does not apply to every house with a crack in it. Plenty of slabs have cosmetic cracking, minor stable elevation variation, and no need for structural work at all. Establishing which situation you are in is the job of the evaluation, not of a photograph.

For the full service picture, see slab foundation repair.