Do tree roots really damage foundations, driveways and pipes? A Queensland guide

A crack appears in the driveway, there's a big fig two doors down, and the tree gets the blame. Sometimes that's fair. But roots are blamed for a lot of damage they didn't cause, and plenty of trees are removed for problems that removal doesn't fix. Here's how it actually works.

How roots really behave

First, the myths. Roots don't seek out pipes to smash, and they don't dive under houses looking for footings. Most tree roots live in the top 600 millimetres of soil, spreading wide rather than deep, following moisture and oxygen.

That behaviour explains almost every real problem they cause:

• Paths and driveways: shallow structural roots thicken as the tree grows and lift whatever sits on top of them
• Pipes: roots can't break a sound pipe, but a pipe that's already leaking is a moisture beacon. Fine roots enter at the existing crack or joint and expand
• Slabs and footings: in SEQ's reactive clay soils, the bigger effect is indirect. A thirsty tree dries the clay under one side of a structure, the clay shrinks, and the structure settles unevenly

That last one surprises people: the damage mechanism is often the soil moving, not the root pushing.

The usual suspects

Species matters enormously. Figs (including the beautiful Moreton Bay fig), camphor laurels, poplars, umbrella trees and large gums are the classic offenders near structures. Umbrella trees in particular were planted next to half the houses in Queensland decades ago and their roots go straight for drains. A jacaranda or a bottlebrush the same distance away is rarely a problem.

Distance matters too. As a very rough rule, trouble starts when a large vigorous tree stands closer to a structure than its mature canopy width. A big fig ten metres from the house is usually fine. The same fig two metres from the pool shell is a plan waiting to unfold.

What actually fixes root problems

The important thing to know: cutting down the tree does not remove the roots, and dead roots stop holding reactive clay stable. Removing a large thirsty tree next to a house on clay can cause its own round of soil movement as moisture levels rebalance. That's not a reason to keep a dangerous tree. It is a reason to get advice specific to your soil and structure first.

Real options, from lightest to heaviest:

• Pruning roots at a trench line and installing a root barrier between tree and structure
• Relining or repairing the leaking pipe, which removes the attraction entirely
• Redirecting paths and driveways, or bridging them over structural roots
• Removal and stump grind, for the wrong species in genuinely the wrong place

Root pruning has limits: cut too much of the structural root plate and you've destabilised the tree. That's an assessment call, not a chainsaw call.

If you're planting

The cheapest root problem is the one you never plant. Keep large vigorous species at least their mature height away from structures, choose small natives near paving and pools, and never plant an umbrella tree anywhere, which is advice the whole of Queensland learned the hard way.

Worried about a specific tree?

Send us a photo of the tree and the structure it's near, plus your suburb. We'll tell you honestly whether it's a real risk, a watch-and-wait, or a myth doing the rounds of your street. Assessments are part of every free quote.