The Test in One Sentence
Will the slab lift as a piece?
That is the whole question. Foam raises concrete; it does not repair concrete. A slab that is intact enough to be raised as a unit is a candidate. A slab that has lost structural integrity is not, no matter how much foam is injected beneath it. Our concrete leveling page covers the service.
Good Candidates
Sunken sidewalk and walkway panels. Especially where a lip has formed at a joint. This is one of the most common applications and one of the most worthwhile, because a raised edge across a walking route is a genuine trip hazard.
Uneven driveway slabs. Including approaches and aprons where vehicles catch, and panels that have dropped relative to the garage threshold.
Settled patios. Particularly where the patio has dropped away from a door threshold, creating a step that was not there originally.
Pool decks. Panels that have settled around coping. Common, addressable, and worth attending to given the surface people walk on barefoot.
Concrete steps and landings. Where they have separated from a structure or settled relative to it.
Garage slabs. Where the slab has dropped at the entry or across a section.
The common factor: the concrete may be weathered, may be aged, may have a crack or two, but it holds together as a slab.
Poor Candidates
Concrete broken into many fragments. Multiple intersecting cracks mean the slab will move as pieces rather than as a unit. The result is an uneven lift that looks worse than the original settlement.
Heavy spalling. Where the surface is delaminating and aggregate is exposed across a large area, the concrete has deteriorated as a material.
Extensive map cracking. A network of fine cracking across the surface, often indicating a broader material problem.
Exposed, corroded reinforcement. Where corroding steel has caused widespread concrete damage.
Concrete too thin for its current load. A slab originally poured for foot traffic now carrying vehicles is a different problem.
Slabs over an active washout. Technically liftable, but without addressing the water source the void reforms. The cause comes first.
Our guide on leveling versus replacement covers the decision when a slab falls into this group.
Condition Factors Assessed
| Factor | What it affects |
|---|---|
| Slab thickness | Whether it can take the lifting force as a unit |
| Crack count and pattern | Whether it moves as a piece |
| Surface condition | Whether the material has deteriorated |
| Reinforcement | Presence and condition |
| Void extent | Volume of material required |
| Height of drop | How much lift is needed |
| Subgrade condition | Whether the cause is still active |
| Utilities beneath | Safety and port placement |
| Access | Equipment reach and hose runs |
We would rather tell you no
Lifting a slab that will not hold is a poor outcome for both parties: you pay for a result that fails and we have done work we cannot stand behind. If the assessment says replacement, that is what the assessment says, even though the lifting job would have been easier to sell.
Trip Hazards Get Priority
Where a settled panel has created a lip across a walking route, that is worth addressing promptly regardless of aesthetics. A raised edge on a public sidewalk or a route across a property is a real risk, and in some circumstances a liability one.
Trip-hazard remediation is often a small job: a single panel, a modest lift, and a couple of hours. It is worth asking about even where the wider flatwork is not a priority.
What Settlement Tells You About the Cause
Before committing to a lift, it is worth asking why the slab dropped.
- Subgrade erosion and washout. Water tracking under the slab carrying fine material away. Look for a downspout, an irrigation line, or a grading issue nearby.
- Poor initial compaction. Fill placed during construction still consolidating.
- Expansive clay shrinkage. Seasonal, and sometimes partly reversible.
- Tree roots and organic decay. Displacement or void formation.
Where the source is visible, addressing it alongside the lift is the difference between a durable result and a repeat visit.