Driveway settlement

Frequently not, and that is the most useful thing this page can tell you. A driveway that has dropped has usually lost support underneath, and if the concrete itself is intact the slab can often be lifted back rather than removed and repoured.

The decision turns on the condition of the concrete rather than on how far it has dropped. Sound concrete that has moved is a lifting candidate. Concrete that has broken into pieces, or whose surface is failing as well, is a different conversation.

What it is

Driveways settle where the ground beneath them changes volume or gets carried away. The classic locations are telling: right at the garage entry, at the apron where the driveway meets the street, and in a line across the drive where a utility trench was backfilled.

Those locations share a cause pattern. Each is a place where soil was disturbed and put back — around the foundation, at the road edge, over a service run — and backfill that was not compacted to the same density as undisturbed ground continues to consolidate for years.

Water is the other half of the story. Roof water discharging beside the drive, or surface water running along its edge, can move fine material out of the base and leave a void the slab eventually drops into.

What seeing this cannot establish

• How far a driveway has dropped says nothing about whether it can be lifted. A slab that has settled several inches but is in one piece is often a better lifting candidate than one that has dropped half an inch and cracked in four directions.
• Settlement at the garage entry cannot be distinguished from foundation movement by looking at the driveway. The driveway slab and the foundation are usually separate elements, and confusing them is common in both directions.
• The presence of a void beneath cannot be confirmed from the surface. Tapping and sounding give hints; they are not measurements.

What this can be associated with

Candidate explanations, not findings. Nobody can establish which applies to your concrete without seeing it.

• Backfill around the foundation consolidating over years, which is why the garage entry is such a common location
• Utility trench backfill settling, which can be associated with a drop in a line across the drive
• Roof or surface water discharging beside or onto the drive, which can move base material
• Base material that was thin, uncompacted, or placed over soft ground at construction
• Soil moisture cycling in clay-rich ground, which can be associated with seasonal or progressive volume change
• Heavy vehicle loading on a slab poured for cars — delivery trucks, dumpsters, RVs

What you can safely check yourself

• Photograph the drop from the side at ground level, with a straightedge or long level bridging the low area. Side-on photographs show elevation change that overhead ones hide.
• Note exactly where the drop is: at the garage, at the street, in a line across, or at one corner. Location is the strongest clue available to you.
• Tap the low area with a hammer handle and compare the sound to a part of the drive that has not moved. A hollow note can be associated with a void, though it does not confirm one.
• Check whether the slab is in one piece across the settled area or broken into sections. This is the observation that most affects your options.
• Watch where water goes in heavy rain and photograph it. Water pooling at the low point tells you the problem is now self-reinforcing.
• Look at whether the drop has created a step at the garage door, and measure it. That step is both a trip hazard and a water path into the garage.

When this is frequently cosmetic

• A small, stable drop away from the house that does not pond water and creates no trip step
• A settled apron at the street edge with no drainage consequence and no vehicle scraping

When professional evaluation matters more

• Water now runs towards the house or ponds against the garage or foundation
• There is a step at the garage door big enough to catch a foot or scrape a vehicle
• The drop has increased between dated observations
• The slab has broken into several pieces across the settled area
• The area sounds hollow across a broad extent, suggesting significant void
• Settlement appears alongside cracking in the house itself, which is a reason to ask about the foundation as well as the drive

When replacement enters the conversation

• The slab is broken into multiple pieces across the settled area rather than displaced in one piece
• The surface is deteriorating as well as settled, so lifting would restore height on concrete that is failing anyway
• The drive is at or near the end of a normal service life and multiple areas have moved
• The base or subgrade needs rebuilding, which lifting does not do

Evidence worth having before you ask for estimates

Every item here is something you can produce without tools or risk, and every one of them makes an estimate more accurate.

• Side-on photographs with a straightedge bridging the low area
• A measurement of the maximum drop, and of any step at the garage
• Photographs showing whether the slab is intact or broken across the settled area
• A note of where roof water and surface water discharge
• Whether any heavy vehicle has used the drive that it was not built for
• Dated photographs if you have any history at all

Questions to ask whoever comes out

• Is this slab a lifting candidate, and what specifically makes you say yes or no?
• What do you think caused it, and does your proposal address that or only the height?
• If you lift it, where will the drilled holes be and what will they look like afterwards?
• What happens to the drainage once the height is restored?
• If lifting does not hold, what is the next step and what does it cost?
• Are you pricing the apron and the garage entry separately, and who is responsible for the section in the public right of way?

Where estimates for this commonly differ in scope

These are the places two prices for apparently the same work stop being comparable.

• Lifting and replacement estimates get compared as if they answer the same question. They restore the same height by very different means with very different lifecycle profiles.
• The apron at the street is often in the public right of way and may be subject to municipal requirements. Estimates differ on whether it is included and who permits it.
• Drainage correction is frequently the thing that stops it happening again and is frequently excluded. Ask whether it is in the price.
• Void filling and lifting are related but distinct. An estimate may include stabilising the base, may include only raising the slab, or may include both.

Who tends to do this work

• A concrete leveling specialist
• A residential flatwork concrete contractor
• A drainage contractor or landscaper who does grading

ConcreteOwner does not inspect, certify or approve contractors. This describes which trade usually holds this work, not a recommendation of anybody in particular.