· Michael Blair
A settled walkway or driveway panel is often lifted rather than replaced. It costs considerably less, takes hours rather than days, and the slab is usable immediately. It also does not work in every case.
How lifting works
Small holes are drilled through the slab and material is injected beneath it under pressure, filling the void and raising the concrete back to level.
Mudjacking uses a cement slurry; polyjacking uses expanding polyurethane foam. Foam is lighter, uses smaller holes, cures in minutes and does not add weight to soil that has already proven it cannot carry the load.
When it is the right answer
The slab is structurally sound — settled as a unit rather than broken into pieces. The void beneath is from soil consolidation, erosion or a washed-out base rather than ongoing movement.
It suits driveway panels, walkways, patios, garage floors, pool decks and steps that have dropped relative to their neighbours.
- Slab intact, settled as a unit: lift
- Slab broken into several displaced pieces: replace
- Crumbling, spalling or delaminating surface: replace
- Ongoing active soil movement: fix the cause first
- Slab that was always too thin for its use: replace
When it is not
A slab that has already broken into multiple pieces cannot be lifted as a unit, and lifting it makes the breaks worse. Surface deterioration is not fixed by raising it.
And if the cause is still active — a leaking downspout washing out the base, or a drainage problem saturating the clay — lifting without fixing that buys a year or two.
Fix the water first
In Middle Tennessee the usual cause of a washed-out base is water: a downspout discharging beside the slab, a gutter overflowing, or grading that sends runoff under it.
A competent contractor asks where the water goes before quoting. One who does not is selling you a repeat.