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Tree roots lifting a section

Cutting the roots may destabilize the tree. Ramping or replacing that section around the root is usually the better trade, and the tree assessment comes first.

Quick answerRoots grow toward the moisture that collects under a slab and lift it as they thicken. The obvious fix, cutting the root, can weaken or destabilize the tree, and a tree that falls is a far bigger problem than a raised walk. Have the tree assessed first. Then the usual options are grinding or ramping the raised edge, or replacing that section so it bridges or works around the root.

A lifted slab is a trip hazard today and a cracked slab tomorrow. But the order matters: decide what the tree can tolerate, then decide what to do with the concrete.

A tree growing on a sidewalk, pushing against the paving
A tree pushing against the sidewalk around it. Decide what the tree can tolerate before anyone touches the concrete. Photo by Sean Foster on Unsplash.

1Why roots lift concrete

  • Moisture. The soil under a slab stays damper than the open ground around it, so roots spread there.
  • Thickening. Roots grow in diameter every year. Even a slow change is enough to lift a slab edge.
  • Shallow base. A thin base leaves little room between the root zone and the concrete.

2How to check what you’re dealing with

  1. Measure the liftNote how high the raised edge sits above the next slab. Even a small lip is a trip hazard on a walk.
  2. Find the treeIdentify which tree the root comes from and how close it is. Roots can travel well beyond the canopy.
  3. Check the tree’s healthDead branches, a lean, or fungus at the base are reasons to call an arborist before anyone digs.
  4. Check ownershipIf it’s a street tree or a neighbor’s tree, ask the owner or your city before cutting anything.

3Fixing it

Do it yourself

  • Mark the raised edge so nobody trips
  • Have the tree assessed before any root work
  • Keep heavy vehicles off the lifted section

Hire a pro

  • Grinding or ramping the raised edge
  • Removing and repouring the section
  • Root work, only on an arborist’s advice
  • Installing a root barrier where suitable
Don’t cut first

Cutting a large structural root close to the trunk can weaken a tree’s anchorage. Get the tree assessed before anyone cuts.

4What drives the cost

Grinding a lip is a small job. Replacing a section adds tear-out, haul-away and a new pour, and possibly a reroute of the walk. An arborist’s assessment and any root work or barrier are separate costs. Ask whether the concrete contractor will coordinate with the tree work.

Concrete cost

Slab heaving over a root?

Talk to a concrete contractor about ramping or replacing the section once the tree has been looked at.

877-360-4657

5Questions

Can I just cut the root?

Not without an assessment. Some roots are safe to remove; others hold the tree up. An arborist can tell you which.

Will a new slab just lift again?

It can. That’s why replacements are often designed to bridge or curve around the root, sometimes with a root barrier.

Who pays if it’s a street tree?

That depends on your city. Ask your local public works or parks department before doing any work.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.

877-360-4657