Tree roots are lifting my pavers. Can I fix the walkway without killing the tree?

Why roots lift pavers

Tree roots grow toward water and air, and the gravel base under a paver walkway holds both. Roots run along the top of the soil just under the base, thicken each year, and eventually push the pavers up in a line or a hump. Ficus, liquidambar, jacaranda, pines and many eucalyptus are frequent offenders in North County yards; drought-stressed trees send roots even farther in search of irrigation.

The paver's advantage is that it fails gracefully. A concrete slab cracks and tilts and has to be cut out; pavers simply rise, and can be lifted and reset.

Option one: raise the surface over the root

Where the root is already established and the grade allows it, the simplest fix is to lift the pavers over the affected area, add base material so the walkway rides above the root with a few inches of cushion, and re-lay the pavers with a gentle transition to the surrounding level. The root is left intact with room to grow for some years. The trade-off is a slight rise in the path, which we blend over several feet so it is not a trip edge.

Option two: move the path

If the walkway passes close to the trunk, rerouting it a few feet farther out often solves the problem for the life of the tree, and the curve around a mature tree usually looks better than the straight line that was there. The old alignment becomes a planting bed with mulch over the roots, which the tree prefers anyway. This is the long-term answer when a tree is large and valued.

Stepping stones set in gravel or groundcover are another way to cross a root zone: each stone sits on its own small pad, and they can be shimmed or shifted as roots move without disturbing a whole field. Our answer on stepping stone and gravel paths covers how to set them.

Option three: limited root pruning, with an arborist

Small roots, roughly finger-thick or less, can usually be cut at the edge of a walkway without harming a mature tree. Larger roots are different. Roots thicker than about two inches, or those close to the trunk, are structural; cutting them can cause the tree to lean or fail in wind and opens it to decay. For anything beyond small roots we ask a certified arborist to assess the tree first and, if pruning is approved, to do it or supervise it.

Root barriers, which are rigid panels installed vertically along the walkway edge, can redirect new roots downward. They work best when installed with a new path before roots have arrived, and they are no substitute for giving the tree space.

What we would not do

Trees are the slowest thing in the yard to replace. Pavers can be lifted in an afternoon. When they conflict, we fix the pavers and let the tree be a tree.

• Cut a large root to flatten a walkway without an arborist's opinion.
• Pour concrete over a root zone; it fails the same way and is far harder to fix.
• Grind a lifted paver edge down; it looks worse and the root keeps coming.
• Remove a healthy mature tree for a path that can simply be moved.

Related questions