The stone is almost never the problem
When a paved area drops, the instinct is to look at the pavers. It is the wrong place to look. Concrete pavers are rated for decades of traffic and they outlast the base they sit on by a wide margin, which is why a settled driveway almost always goes back down using the same stone that came up.
What has failed is underneath: a layer of compacted granular that was either built too thin for what crosses it, or has had its fine material carried away by water. Both leave something closer to loose gravel, and loose gravel compacts under load.
Cause one: the base was never deep enough
A pedestrian walkway can live on about 150 millimetres of well compacted granular. A driveway carrying a car wants closer to 300, and anything taking a delivery van or a bin truck wants more again.
Surfaces built as a weekend job, or by an installer working to a price, frequently sit on a few inches of screening raked level over clay. They look identical on day one. They fail in wheel tracks within a few seasons, because that is where the load concentrates.
You can often tell this one by its pattern: two parallel ruts where the car parks, with the rest of the surface still true.
Cause two: water is taking the base away
This is the commonest cause we open up. Water moving through a base carries out the fine material that locks the stone together, and it goes somewhere specific rather than everywhere at once.
- A downspout discharging onto the surface, which delivers a roof worth of water to one small spot in minutes.
- A lawn or garden grading back toward the paving rather than away from it.
- A perimeter with no edge restraint, letting the field spread until the joints are wide enough to move sand through.
The tell is a line of empty joints running from where water arrives to where it leaves. Refilling that line without changing the run is a repair with a known expiry date.
Cause three: frost, but only where water sits
Freeze and thaw gets blamed for most of this and deserves some of it, but it needs water to work with. A base that drains takes decades of winters without complaint. One that holds water expands every time it freezes and leaves a void every time it thaws.
That is why frost damage shows up as lifting rather than sinking, and why it is worst on shallow bases over clay. Fixing it means giving the water somewhere to go, not simply adding depth to a layer that still holds it.
What each one costs to correct
A surface re-level, where the existing base is sound and just needs re-grading, runs roughly $10 to $18 per square foot. A small single settled area starts around $800 including the visit.
Where the base has to be dug out and rebuilt, the number moves up because it is materials, labour and disposal rather than labour alone. Where drainage has to change as well, that is quoted on its own line so you can see the two costs separately.
When not to repair at all
If the base has failed across most of the area rather than in patches, staged repairs mean paying mobilisation several times over and disturbing ground that is about to need the same treatment. A full restoration is usually cheaper at that point.
And if the pavers themselves are flaking in layers from de-icing salt, relaying them puts failing stone back down. That is the one case where replacement genuinely beats repair, and we would rather say so on the visit than after the surface is up.