How Concrete Lifting Works: A Step-by-Step Guide for Homeowners

Concrete lifting sounds almost too good to be true — drill a few holes, inject some material, and a sunken driveway rises back to level in a couple of hours. But it really works, and understanding the process helps you know what to expect and how to evaluate whether a contractor is doing it right.

The Two Methods: Mudjacking vs. Polyurethane Foam

Both methods share the same principle — injecting material beneath a sunken slab to fill voids and raise the concrete — but they use different materials with different characteristics.

Mudjacking (Traditional Method)

Mudjacking uses a mixture of soil, water, and portland cement pumped beneath the slab at high pressure. The slurry fills voids and the pressure lifts the slab. It's time-tested (used since the 1930s), lower cost than foam, and effective for large-scale projects. Downside: the material is heavy (adds weight to the subbase) and takes 24 hours to cure before vehicle traffic.

Polyurethane Foam (Modern Method)

Two-part expanding polyurethane foam is injected through smaller holes. The chemical reaction between the two parts creates expanding foam that fills voids and lifts the slab with precision. Foam is lightweight (adds almost no weight to the subbase), cures in minutes, and allows for more controlled, incremental lifting. Downside: costs more than mudjacking.

The Process, Step by Step

Step 1: Assessment

A technician walks the area, probes for voids, measures the elevation difference, and identifies the cause of settlement. This assessment determines hole placement and material quantity. A proper assessment takes 15–30 minutes for a typical driveway.

Step 2: Drilling

Holes are drilled in the concrete at strategic locations — typically in a grid pattern or along the edge of the void. For mudjacking, holes are about 1.5–2 inches in diameter. For foam, 5/8-inch holes are sufficient. Hole placement matters enormously — random placement produces uneven lifting.

Step 3: Injection

Material is injected under controlled pressure. The technician monitors the slab's movement constantly, pausing to check level and adjusting injection points as needed. Lifting 1 inch of settlement typically takes 5–15 minutes per injection point.

Step 4: Checking Level

Throughout injection, the technician uses a level to check progress and ensure even lifting. This is a skill — lifting too fast or from the wrong point can crack a slab. Quality work lifts slowly and deliberately.

Step 5: Patching Holes

After lifting is complete, all drill holes are patched with a cement-based filler. The patches are visible but blend with aged concrete over time. Fresh patches are lighter than surrounding concrete initially.

Step 6: Cleanup and Walkthrough

The technician walks the lifted area with you, confirms the result meets your expectations, and advises on return-to-service time (minutes for foam, 24 hours for mudjacking).

What Can Go Wrong (And How to Avoid It)

Concrete lifting done by an inexperienced crew can crack slabs that were otherwise sound. Warning signs of poor technique: drilling too few holes (not enough control), injecting too fast (pressure cracks the slab), not checking level throughout (uneven lift), or over-lifting one section while adjacent sections stay low.

Ask your contractor: how many holes will you drill? How will you monitor the lift? What's your process for checking level during injection? The answers reveal whether they're doing it right.

Bottom Line

Concrete lifting works by filling the void beneath a sunken slab and raising it back to level — either with mudjacking slurry or expanding polyurethane foam. Done correctly by an experienced crew, it's fast, affordable, and long-lasting. Done poorly, it can crack the concrete it was meant to save. Choose a contractor who can explain their technique in detail.