Cracked, lifted or sunken concrete in San Diego can often be fixed by lifting sunken slabs, grinding small offsets, sealing cracks or replacing individual panels. Expansive clay can push slabs up as well as let them drop, so the right fix depends on which happened. Any repair should also fix the water, usually irrigation or drainage.
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Not every cracked or uneven slab needs to be torn out. Depending on the cause, concrete can often be lifted, ground, patched, sealed or resurfaced for less money and mess than replacement. The key is understanding why it failed. In San Diego, that answer usually involves soil moisture, roots or slopes, and a repair that ignores the cause tends to fail again.
Why concrete cracks, lifts and sinks in San Diego
- Expansive clay. San Diego County's geology review places most highly expansive soils on the coastal plain's terraces and mesas, with more in foothill valleys. These soils swell when wet and shrink when dry, which can push slabs up as well as let them drop.
- Irrigation. Lawns and planters watered against a slab edge keep the soil there wetter than under the rest of the slab. Uneven moisture means uneven movement.
- Fill on graded lots. Many hillside and tract neighborhoods were built with cut and fill. Fill that wasn't compacted well can settle, especially near slopes, garages and steps.
- Slope creep and drainage. Slabs near the top of a slope can drift or crack as the slope moves, and winter storms can wash soil out from under edges.
- Tree roots. Street trees and mature yard trees lift walks and driveway edges.
- Shrinkage. Some cracking is normal as concrete dries, especially where joints are far apart or the slab dried too fast.
Repair options
- Slab lifting (mudjacking): a cement-based slurry is pumped under a sunken slab to raise it and fill voids.
- Polyurethane foam lifting: expanding foam injected through small holes. It's light and cures quickly.
- Grinding: shaving down a raised edge to remove a trip hazard when the panel is otherwise stable.
- Crack sealing: flexible sealants keep water out of cracks and joints.
- Patching and resurfacing: repair mortars and thin overlays for surfaces that are worn but structurally sound.
- Section replacement: cutting out broken panels at the joints and repouring.
Lifting versus heaving
Lifting works on slabs that sank. It doesn't help a slab that was pushed up by swelling clay or roots, and lifting the low side next to a heaved panel may just move the problem. If the high side is the problem, grinding, root work or replacing the panel is usually the answer. A good contractor will tell you which you have.
Fix the water first
Any repair plan should include the cause: redirecting sprinklers, converting edge planters to drip, extending downspouts, or regrading so water moves away from the slab. Without that, a lifted slab can settle again or a crack can keep opening.
When it might be structural
Cracks in a patio or driveway are rarely structural. Cracks in a foundation or the house slab, gaps opening between a slab and the house, doors that suddenly stick, or movement near the top of a slope are different. Start with a geotechnical or structural engineer, since that work may need permits and a licensed foundation contractor.
Public sidewalks
In the City of San Diego, homeowners are responsible for many sidewalk repairs in front of their property, and a right-of-way permit is required. Other cities set their own rules.
Questions to ask
- Did this slab sink, or was it pushed up?
- Will you lift, grind, patch or replace, and why?
- What will you change about the irrigation or drainage?
- Is there a warranty if the slab moves again?
Not sure which way to go? Read our guide to expansive soil and concrete in San Diego, or mark your request as urgent and request a concrete repair contractor.
See how it works
Frequently asked questions
Can a slab that was pushed up be lifted back into place?
Not really. Lifting raises slabs that sank. A panel pushed up by swelling clay or roots is usually ground down, has the root addressed, or is replaced, and the soil moisture causing it is corrected.
Is mudjacking or foam lifting better?
Both raise sunken slabs. Cement slurry is the older, heavier method; polyurethane foam uses smaller holes and cures quickly. The right choice depends on the slab, the voids beneath and the soil.
When should I call an engineer instead of a concrete contractor?
If cracks appear in the house foundation or slab, doors start sticking, gaps open between slabs and walls, or concrete near a slope is moving. A geotechnical or structural engineer should look first.
Sources and further reading
- American Concrete Institute (ACI)
- Portland Cement Association (PCA)
- California Contractors State License Board: C-8 Concrete Contractor
- CSLB: License requirement for minor work increases to $1,000 (AB 2622)
- County of San Diego General Plan Update EIR: Geology and Soils (expansive soils)
- City of San Diego Development Services: Information Bulletin 165, Public Right-of-Way Permits
- City of San Diego Transportation Department: Sidewalk maintenance responsibility
- City of San Diego Stormwater
- California Department of Water Resources: Model Water Efficient Landscape Ordinance
- County of San Diego: Excavation Permit Brochure (DigAlert notice)
- DigAlert: Underground Service Alert of Southern California (811)