Tree Roots Lifting Your Driveway or Sidewalk: Options Before Removal

A cracked, heaving driveway doesn't always mean the tree has to go. There are several fixes that keep the tree. But the most common quick fix, cutting the roots and re-pouring the concrete, can make a tree unstable enough to blow over. Here's what to know before you decide.

First, make sure it's really the roots

UF/IFAS points out that concrete often cracks whether or not trees are nearby, and roots tend to grow into cracks that already exist. Thin slabs that weren't built to carry a car can crack on their own. If you can see a thick root running right under the raised section, the tree is probably the cause.

Why cutting the roots is risky

The large roots close to the trunk are what hold the tree up. Cutting them can lead to decline, decay or the tree toppling in a storm, which matters a lot in hurricane country.

UF/IFAS's general guideline is to leave all roots within about five times the trunk diameter. For a tree with a 2-foot-wide trunk, that means no cuts within 10 feet of the trunk. Cutting closer than that raises the risk, especially on wet, compacted or shallow soils, and leaning trees are poor candidates for root pruning at all.

Options that keep the tree

• Bridge the roots. Build a section of walkway or driveway that spans over the roots, using metal, wood decking or a concrete ramp that doesn't sit on the roots. The roots don't have to be cut.
• Re-pour over a cushion. Lay 3 to 6 inches of rubber chips or a layer of washed gravel over the roots, then pour the new slab on top. This helps keep roots from pushing directly into the concrete.
• Reinforce the new slab. Rebar in the concrete helps the slab lift as one piece instead of cracking.
• Reroute or reshape. Curve a sidewalk away from the trunk or widen the open space around the tree.
• Switch materials. Pavers, gravel or other flexible paving handle root movement better and are easier to reset.
• Install a root barrier when you rebuild, to guide future roots down and away from the slab. It works best as prevention and still means cutting some roots, so keep it well away from the trunk.

When removal is the honest answer

Sometimes keeping the tree isn't the best choice:

• Fixing the slab would mean cutting large roots close to the trunk.
• The tree is leaning, declining, or has decay in its trunk or roots.
• Roots are threatening your foundation, pool or plumbing, not just the driveway.
• The tree is a short-lived species near the end of its life, such as an older laurel oak.

If removal makes sense, replant with a tree suited to the space, farther from the pavement. See what tree removal costs in DeLand.

Sources: UF/IFAS EP309 (Urban Design for a Wind-Resistant Urban Forest); UF/IFAS Landscape Plants (Gilman): root pruning guidelines, roots lifting sidewalks, bridging roots.