Before anyone digs near roots
Get underground services located before any digging to expose or cut roots. A beforeUdig enquiry brings back the utility owners' plans, generally within two business days, and NZ Arb's Best Practice Guide says below-ground work needs suitable methods to find services and may need the network owner's approval. Don't cut a big root just to see if it helps: losing a main anchoring root can leave a tree unstable.
How roots actually cause trouble
Most of a tree's roots sit in the top layer of soil and spread well beyond the edge of the crown. They grow wherever there's water, air and room, which is why they turn up in some unexpected places.
Drains are the classic case. Roots don't hunt for pipes, but a cracked joint leaks moisture, and a fine root that finds the crack can grow inside and block the pipe. A sound, well-jointed pipe is far harder for a root to get into, so a root-blocked drain is often a broken drain first.
Paths and driveways are next. Roots thicken a little every year, and near the surface they lift light paving, edging and thin concrete, especially close to the trunk.
Foundations are usually about soil, not roots pushing on walls. On clay, a big tree drawing water in a dry summer can shrink the ground, and light footings or paths on it can move. Taking a big tree out of clay can let the ground swell back, so get advice before removal as well as before root work.
Finding the cause, in order
Record what you see
Photograph cracks, lifted paving or slow drains with the date, so you can tell whether it's getting worse.
Get the drain inspected
A drainlayer or plumber can put a camera down the drain and show you where roots are getting in, and whether the pipe was already broken.
Have cracks assessed
For cracks in walls or floors, a building surveyor or engineer can tell you whether it's the soil, the tree or something else entirely.
Bring in an arborist
An arborist can tell you whose tree the roots belong to, how far they're likely to run and what root work the tree can tolerate. For a dispute or a council application, ask about an arborist report.
Check the rules before root work
Roots can be protected along with the tree, so ask the council before any cutting near a listed tree.
When the roots belong to a protected tree
In Auckland, the notable tree rules cover the tree's protected root zone as well as the tree itself, and work in that zone that the plan doesn't otherwise provide for needs resource consent. For drains under a notable tree, the plan sets standards for trenchless methods deeper than 1m, including direction by a qualified arborist, so ask the council what your job needs before the drainlayer starts.
Christchurch's District Plan covers gardening under its significant trees as well as pruning and removal. For council trees in Tauranga, Asset Owner Approval from the Urban Forest team covers root disturbance as well as pruning and removal.
Kauri need particular care, because kauri dieback infects the tree through its roots. DOC says spread is reduced by not moving soil around kauri roots, and since 2 August 2023 earthworks within a kauri hygiene zone, three times the radius of the canopy dripline, need an earthworks risk management plan. Our kauri dieback guide explains the hygiene rules, and the notable trees guide covers listings.
When the roots are the neighbour's, or the council's
Neighbour tree problems fall under the Property Law Act 2007, and Community Law says it's always best to talk to your neighbour first. If roots or branches encroaching from next door damage your property, it says you can claim the cost of removing them and of repairs in the Disputes Tribunal or the District Court, and the Disputes Tribunal lists tree roots damaging drains among the disputes it hears.
A District Court order to trim or remove a neighbour's tree is a bigger step. Interference with drains is one of the listed problems a judge can consider, but Community Law notes judges are cautious about making these orders. Our neighbours' trees guide walks through it. This is general information, not legal advice.
If it's a street tree, report it to the council rather than cutting its roots. Councils manage their own trees, and Hamilton City Council, for one, will inspect a public tree on request.
Your part, and the arborist's
You can
- Photograph and date cracks, lifted paving and slow drains.
- Get the drain camera-inspected before blaming the tree.
- Keep cars and heavy loads off the root area of trees you want to keep.
- Plant new trees well away from the house and drains, with room to reach full size.
- Talk to the neighbour first if the roots come from their side.
Leave to an arborist
- Working out whose roots they are, and how far they run.
- Root pruning, and whether the tree can stand it.
- Root barriers alongside a drain, a path or a wall.
- Removal, and what that may mean for the soil around it.
- Reports for a dispute, an insurer or the council.
Tree roots near your house, drains and paths: what to do next
We'd get the drain inspected and any cracks looked at before blaming the tree, because the fix for a broken pipe is a new pipe. If the roots really are the problem, we'd ask an arborist what root work the tree can take before anyone cuts, and check the council's rules first. Taking a big tree out of clay soil is a call we'd make with an engineer's advice, not on a hunch.
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