A hollow spot under the driveway edge is fixed by a concrete contractor who does slab leveling and flatwork repair, in most cases with polyurethane or cementitious grout injection that fills the void and lifts the settled slab back to grade. When the edge has already cracked off or the slab is beyond lifting, the same contractor cuts out that section and re-pours it on a properly compacted base. In Syracuse, that decision usually comes down to whether water has been running under the apron for years or the slab was poured thin over a shallow base to begin with.
What Causes a Hollow Spot at the Driveway Edge
Your driveway sits on a sub-base of compacted crushed stone, usually 4 to 6 inches of it, under a slab that should be 4 to 5 inches thick. The hollow forms when that stone layer loses support, the soil beneath it settles, or fine material washes out and leaves an air pocket the slab is bridging.
The usual culprits on Onondaga County properties:
- Downspouts and sump lines discharging within a few feet of the driveway edge, sending water under the slab instead of away from it.
- Grading that slopes toward the driveway instead of away, so snowmelt and rain pool at the edge and soak in.
- A base dug too shallow. Frost gets down around 42 inches here. A base that stops well above that heaves and settles season after season, and the edge is the first place it shows.
- Trench backfill from a utility line or sewer repair that was never compacted properly.
- Edge loading, tires running the same 12 inches of slab every day, especially where the driveway meets the street apron.
Road salt and freeze-thaw don't create the void, but they widen it. Water sits in the hairline crack at the edge, freezes, pushes the slab up, and drops it back a little lower each spring.
Signs the Void Is Getting Worse
Walk the edge in boots and listen. A dull, drum-like sound means the slab isn't touching base. Then look for:
- A crack running parallel to the edge, 6 to 18 inches in from the face
- Spalling or scaling on the edge face where salt sits
- Water that puddles at the edge and drains away slowly
- A slab that rocks slightly when a car crosses it
- Joints that have opened wider than a quarter inch
Any of these means water is already moving through. Waiting a season usually costs more than the injection would have.
Who to Call, and Who Not To
Call a concrete contractor that performs slab leveling, not a handyman with a bag of patching mix. Surface patching over a void is cosmetic; the slab keeps settling and the patch pops off within a winter or two. This is flatwork, not a patching job: it needs injection ports, a pump, and a judgment call about whether the slab is worth saving.
If the hollow sits over a broken water or sewer line, that's a plumber first, then the concrete contractor after the line is repaired.
If the settled edge is the right-of-way apron between your driveway and the street, check with the City of Syracuse or the town, Syracuse, DeWitt, Clay, Liverpool and Salina all have their own rules about who is allowed to work in that strip and what permit is required. We pull the permit as part of the job when the apron is involved.
What's Included in a Hollow-Spot Repair
- Sounding the slab and the apron to map the void, not just the spot you noticed
- 5/8-inch injection holes cored through the slab on a grid
- Polyurethane foam or cementitious grout injected in lifts until the slab lifts to grade
- Crack and joint sealing with a flexible polyurethane sealant
- Edge rebuild with air-entrained 4,000 psi concrete where the face has broken away
- Downspout extensions or a shallow regrade so the water stops going under the slab
- Permit handling for right-of-way apron work
Typical Syracuse Pricing
Concrete Repair & Slab Leveling runs $400 to $2,500 on most residential driveways, with a single apron section at the low end and a full slab with crack sealing and edge rebuild at the high end. A cut-out and re-pour of one edge section typically lands in the same range.
These are planning numbers, not a firm quote. Final cost varies a lot with job size, how deep the void runs, whether the apron needs a city or town permit, and whether the slab is worth lifting at all. We put the number in writing before anyone touches the concrete.
How the Repair Goes
Walk and sound the slab
We mark every hollow section with chalk and check the apron separately
Check the water source
If a downspout or grade is feeding the void, fixing the slab without fixing that is a waste of money
Decide: lift or replace
If more than about a third of the slab is hollow or the edge has crumbled past the rebar, replacement is the cheaper long-term answer, and we tell you that in writing, not after the invoice
Inject
Holes cored, foam or grout pumped in lifts, slab monitored back to grade
Seal
Cracks and joints get flexible sealant. Edge damage gets cut back to sound concrete and rebuilt
Clean up and check the drainage
The crew leaves with the water pointed away from the slab
Why Syracuse Driveways
We pour and repair driveways for this specific climate, base dug and compacted for the 42-inch frost depth, air-entrained 4,000 psi mix that holds up to road salt from November through April, and control joints cut on a plan instead of wherever the crew stops. That matters for repairs too: when we inject a slab, we're judging it against what a slab in Central New York should have been built like in the first place. If a repair beats a replacement, we say so in writing and stand behind the work.
We work in Syracuse and the surrounding towns, DeWitt, Clay, Liverpool, Baldwinsville, Fayetteville, Camillus.
Hollow edge, cracking apron, a slab that rocks if you pull in? Call Syracuse Driveways for a free quote and a straight answer on whether your slab can be lifted or needs to come out.