Void filling and lifting
Material is injected beneath the slab to fill the void and raise the concrete back toward its original elevation.
Settled concrete · Greater Burlington
Concrete leveling and slab repair: sunken slabs, walks and garage floors
A sunken slab is a symptom. Concrete settles because the material beneath it moved, washed out or was never compacted, so lifting the slab without asking why it dropped tends to buy a few seasons rather than a repair.
No phone call needed.
What this service includes
Walkways, patios, garage floors, steps and basement slabs settle when the soil beneath loses support: poor compaction at backfill, water washing fines out, a leaking downspout or drain, or frost action over repeated Vermont winters. Lifting methods can raise the slab back toward level, but the void and the water that created it need addressing or the slab settles again. A slab dropping next to a foundation deserves a foundation evaluation, not only a lift.
Common reasons homeowners call
Problems this service can fix
A walkway or patio that now pitches toward the house
A trip hazard where two slabs meet
A garage floor that has dropped away from the apron
Steps pulling away from an entry
A basement floor section lower than the rest
Gaps under a slab visible at the edge
Pooling water where the surface used to drain away
Repairs and systems
Repairs and systems
Drainage correction
Downspouts, surface grade or a failing drain that washed out the base are corrected so the support material is not removed again.
Joint and crack sealing
Open joints that let surface water reach the sub-base are sealed after lifting so the cycle does not restart.
Slab replacement
Where concrete is broken beyond lifting, or the base needs rebuilding, replacement is the more durable option.
Interior slab repair
Settled or cracked basement floor sections are evaluated for water, fill and structural causes before a cosmetic repair.
Foundation evaluation
Settlement next to the foundation is assessed to determine whether the slab alone moved or the structure is involved.
Matching the option to the condition
Slab repair options by condition
A sunken slab usually means something washed out or settled beneath it. Find that first.
| Condition | Option | What to confirm first |
|---|---|---|
| Slab dropped into a void | Void filling and lifting | Cause of the void |
| Water washing soil out | Drainage correction | The water source |
| Open joints and cracks | Joint and crack sealing | That the slab is stable |
| Badly broken slab | Slab replacement | Base preparation |
| Slab tied to foundation movement | Foundation evaluation | Whether the foundation is moving |
- 01
How much the slab has dropped and in what direction
- 02
Whether the movement is ongoing or historic
- 03
What is beneath the slab and how it was backfilled
- 04
Roof runoff, downspouts and drains near the settled area
- 05
Whether the adjacent foundation shows related movement
- 06
Utilities beneath the slab that could be affected
Your estimate
What is included in the plan
Find the washout
Concrete rarely settles without a reason, and a downspout, a leaking drain or uncompacted backfill is usually still there after the lift.
Lift is not guaranteed to be perfect
Reaching approximately level is realistic, and returning a broken, spalled slab to a like-new surface generally is not.
Near-foundation settlement
A slab dropping right beside the house may reflect backfill settlement or something structural, and those are different projects with different prices.
Frost
Repeated freeze-thaw in Vermont moves poorly drained material, and drainage correction is part of making the repair last.
Already have an estimate?
Compare the complete concrete leveling & slab repair scope.
Sources and Vermont specifics
Telling shrinkage from settlement before paying to lift a slab
InterNACHI's guidance separates shrinkage cracks from settlement cracks by movement: shrinkage cracks show no vertical displacement, and the cracking is inevitable and expected in slabs and foundation walls, while cracks with vertical displacement point to settlement or heave. A slab that is only cracked may need sealing, not lifting. A slab that has dropped on one side of a crack needs to be measured, and its cause found, before any material is injected under it.
Ask the contractor to measure the drop across each crack in inches, to say why the ground moved, and to say what will stop it from moving again. Along Lake Champlain, deposits of sand, silt and clay sit over till, so voids and soft spots can vary within one yard. A lift that ignores the cause of the void can be undone by the next wet spring.
Sources: InterNACHI, Shrinkage Cracks in Concrete; UVM PLACE Program, Burlington surficial geology. Checked September 26, 2026.
Common questions
Concrete Leveling & Slab Repair FAQs
Why did my walkway sink but the house did not?
Exterior flatwork usually sits on backfill rather than undisturbed soil or a footing. That fill settles, and water moving through it can carry fines away. The house sits on a footing below frost depth, which is why the two can move independently.
Is concrete leveling permanent?
It lasts as long as the support beneath the slab does. If the cause was a downspout discharging under the slab or a failed drain, and that is corrected, a lift can hold for years. If the cause is left in place, the slab settles again.
Should a sunken basement floor worry me?
It deserves a look. A basement slab is usually not structural, so a dropped section often reflects fill or water below rather than a failing foundation. But settlement combined with wall cracks or movement needs a structural evaluation.