A panel that has lifted at the edge closest to the trunk
Root damage does not look like a crack running across the slab. It looks like one panel sitting higher than the panel next to it, usually along the joint nearest a big tree. Step on the raised edge and it does not rock the way a settled corner does. It is simply higher, because something under it grew.
The panel itself is usually fine. What moved is the ground it is sitting on, pushed up from below by a root instead of washed out or settled the way most base failures go.
- A joint or crack where one side sits visibly higher than the other, closest to a trunk
- The lift follows the direction of the tree's root flare, not the shape of the slab
- Concrete on the far side of the slab, away from the tree, still sits flat
Why a root pushes a slab up instead of growing through it
Concrete is far stronger in compression than a root is in growth pressure, so a root does not punch through solid concrete the way people picture it. What it does instead is grow sideways under the slab edge, in the loose, aerated soil right at the surface where roots want to be anyway, and get thick enough over years that the slab above it has nowhere to go but up.
Maples, willows, and other shallow rooted, water seeking trees cause most of this, because their root systems stay close to the surface instead of running deep. A tree with a deep taproot rarely causes the same problem.
How close a tree has to be before it becomes a problem
There is no fixed distance that is safe. It depends on the species, the age of the tree, and how much of its root system already runs under the pour before the concrete goes down. A young tree planted well clear of a driveway can still cause a lift ten or fifteen years later, once its roots have had time to spread that far.
The panels closest to the trunk are the ones to watch. If a driveway or walkway was poured near a mature tree that was already there, that is where a lift is most likely to show up first.
Cutting the root does not put the slab back down
Cutting the root that caused the lift stops it from pushing further, but it does not lower the slab that is already raised. The concrete stays where it settled, and depending on how the root grows back or how close a neighboring root runs, the same panel can lift again.
Grinding the raised edge down can smooth a trip hazard on a small lift, but it does not address the root underneath, and it thins the slab at exactly the spot already carrying the most stress. For a lift of any size, the panel usually has to come out.
What replacing that section actually involves
Fixing a root lifted panel means taking that section out and dealing with the root in the base before a new panel goes back in. That is the same tear out and replacement work we do for any settled or broken slab, just triggered by a root instead of soft ground, and it is covered in full on our tear out and replacement page.
If the tree is still growing and still close, we will tell you honestly whether the new panel is likely to see the same problem again in a decade, and what a wider gap at that joint buys you.