Intact slab with a localized low area
- Likely next step
- Evaluate slab lifting
- Why it matters
- Preserving an intact slab may avoid demolition and replacement.
How Do You Repair Sunken Concrete?
Updated September 2026
Sunken concrete repair may involve lifting an intact slab with cement-based grout or expanding polyurethane foam, stabilizing a void without raising the slab, or replacing concrete that is too damaged to lift. Sunken, sinking, and settled concrete generally describe a slab that has moved downward after losing support. The right method depends on why the slab lost support, whether movement is continuing, and whether the slab remains intact enough to lift.
Start with the condition, not the product
Choose a sunken concrete repair method based on the slab's condition and the reason it settled. Those conditions determine whether lifting, stabilization, or replacement deserves evaluation.
Void beneath a level slab
- Likely next step
- Evaluate stabilization
- Why it matters
- Filling support loss is different from deliberately raising the slab.
Shattered or severely deteriorated slab
- Likely next step
- Evaluate replacement
- Why it matters
- Lifting does not restore concrete that is too damaged to remain intact during lifting.
Continuing erosion or soil movement
- Likely next step
- Correct the cause first
- Why it matters
- Injected material cannot guarantee stable soil or stop ongoing water movement.
Why does concrete sink or settle?
Concrete sinks or settles when the material supporting the slab loses volume, strength, or contact with the concrete. Conditions worth investigating include poorly compacted or disturbed fill, soil drying or shrinkage, erosion or washout, and active water movement from grading, drainage, or leaks. The repair scope should state which condition is known, suspected, or excluded because raising the slab does not by itself stop an active support problem.
- Redirect water before lifting when erosion is contributing
- Investigate sudden settlement near utilities or plumbing
- Document whether movement is continuing
- Confirm that lifting will not create a new drainage or threshold problem
How do you fix a sunken concrete slab?
To fix a sunken concrete slab, first determine whether it needs lifting, stabilization, or replacement. Slabjacking deliberately raises a settled panel by injecting material beneath it, while stabilization fills voids to restore support without necessarily changing elevation.
Cementitious slabjacking pumps a grout mixture beneath the slab. Polyurethane lifting injects a reactive material that expands beneath it.
These methods differ in material, hole size, installation, and project fit. Compare mudjacking and polyurethane foam without treating either method as the automatic choice.
What happens during professional concrete lifting?
During professional concrete lifting, a contractor raises or supports the affected slab while monitoring its movement and nearby transitions.
The exact hole pattern, material, monitoring method, and achievable result depend on the slab and conditions below it.
- Inspect the affected panels and investigate the suspected cause of settlement.
- Establish the intended elevation, transitions, and drainage.
- Drill the planned injection holes through the slab.
- Introduce the selected material gradually while monitoring movement.
- Close the holes and review the repaired joints, edges, thresholds, and drainage.
When should sunken concrete be replaced instead of lifted?
Sunken concrete should be evaluated for replacement when the panel is badly cracked, surface deterioration is deep, the required lift would create binding or misalignment, or the base needs excavation and correction. Ask for lifting and replacement alternatives when the remaining concrete condition is uncertain.
What should a sunken concrete repair quote include?
A sunken concrete repair quote should define the observed condition, intended result, repair method, limits, and responsibility if the slab cannot reach the stated outcome.
- The affected panels, measured height differences, cracks, drainage, and suspected support-loss conditions
- Whether the scope calls for lifting, stabilization, replacement, or correction of water and base conditions
- The target elevation or acceptable tolerance, including thresholds, adjacent panels, and required drainage
- The injection material, anticipated hole size and pattern, monitoring method, and treatment of holes, joints, cracks, and edges
- Protection and monitoring for connected slabs, walls, utilities, finishes, and nearby surfaces
- The fallback plan, price terms, and responsibility if the slab cannot be lifted enough, is raised beyond the target elevation, develops new or wider cracks, or requires additional work
Technical references and limitations
These references support the general repair and planning guidance on this page, but they do not establish requirements for an individual residential project.
The FHWA reference addresses pavement preservation. It provides general context for injection, lifting, and stabilization processes, but it does not establish requirements for a residential slab or replace a project-specific evaluation.
Residential conditions, local codes, product requirements, and structural significance vary. Use a qualified local professional for diagnosis and design where safety or structural performance is involved.