Protecting trees on a building site and when removal needs approval

A tree on a building site is rarely just a landscape feature. It is often a condition of the approval, a neighbour’s concern, a council enforcement issue and a structural problem, all at the same time. The builder who treats it as a bit of garden to be cleared on the first day can find that the approval is in breach before the slab is poured, and that the tree is dead within a year of the excavation beside it.

The problem is that trees do not show the damage straight away. A root system that has been cut, compacted or left to sit in wet spoil can look fine for a season, then decline slowly, drop limbs, or fall in a storm onto the new house. By the time the owner or the council notices, the cause is buried under the footings and the sequence of events is hard to prove. The decisions that protect a retained tree are made in the first week of the job, and they are mostly about paperwork and fencing.

This article covers what a licensed builder needs to know about protecting trees on a NSW building site, and when removing one needs approval. It is not a planning guide, and it does not replace the advice of a qualified arborist or the terms of the consent that applies to your site. It is written to help you ask the right questions before the machine arrives and to recognise when a tree has moved from a protection problem into an approval problem.

Why a tree is a compliance issue, not only a landscape issue

Many trees on residential sites are subject to the conditions of the development consent or the complying development certificate. The conditions may say which trees must be kept, how far works can come from them, what protection must be installed, and who must check it. A condition that is breached on site is a compliance problem for the builder and the certifier, even if nobody has yet noticed the damage.

Councils also have their own controls over trees, and those controls can apply even where the development itself has been approved. The rules depend on the location, the size and type of the tree, and whether the site has any additional overlay. The safe assumption is that a tree is protected until you have confirmed otherwise in writing, and that the cost of checking is much smaller than the cost of an unauthorised removal.

The neighbours matter too. A tree that overhangs the boundary, or whose roots run under the fence, is part of the neighbour’s property and the neighbour’s interests. Damage to a neighbour’s tree during construction is a dispute waiting to happen, and it is one that is usually easier to avoid than to settle.

Find out what is protected before the first machine arrives

Start with the approval. Read the conditions attached to the consent or the certificate, and look for any that mention trees, landscaping, vegetation or protection zones. Note the trees the conditions name, and mark them on the site plan. If the conditions require a tree protection plan, an arborist report, or a sign-off before works start, put those steps on the program before anything else. The guide to construction certificate conditions explains how those conditions are usually presented, and it is worth reading before the first site meeting.

Then walk the site with the plans in hand. Identify every tree on the block, every tree on the neighbour’s land that might be affected, and every street tree on the verge. Check the council’s tree controls for the property, and confirm in writing which trees are protected and what the process is for any work near them. If there is any doubt, ask the council before the work starts rather than after. A written answer is worth more than a verbal one at the time of an inspection.

Make a record of each tree’s condition on the day you start. Photograph the trunk, the canopy and the root zone, note any existing damage or lean, and keep the photos with the job file. That record is the baseline against which any later damage will be measured, and it is the first thing an inspector or a lawyer will ask for.

Protecting the root zone during footings and excavation

The root zone is the part of the ground that the tree depends on, and it extends well beyond the canopy in most cases. The arborist should set the protection zone around each retained tree, and that distance is the boundary for every activity on the site. Inside the zone, no excavation, no spoil, no machinery and no stockpile should be allowed. The fence that marks the zone should be installed before the first machine arrives, and it should be checked at the start of every week.

Footings are the most common point of damage. A trench for a strip footing that is cut through roots can remove a large part of the tree’s anchorage and water supply in one pass. Where a footing must sit inside the zone, the arborist may recommend a different footing design, a pier arrangement that avoids the major roots, or a hand-dug approach. The decision should be made before the trench is marked out, because changing the design once the concrete is delivered is a costly and difficult conversation.

Compaction is the quiet killer. Heavy plant, a loaded truck or a stack of materials on the root zone compresses the soil and drives out the air the roots need. Changes in ground level, including filling and cutting, can also smother roots or leave them exposed to drying and frost. Keep the grade inside the zone as it is, and keep the spoil and the materials outside it.

The Safe Work Australia guidance on excavation work applies to every trench on the site, and that includes the trenches near trees. Excavation near a tree is a hazard to the workers as well as to the tree, because a trench cut beside a large root can collapse without much warning. Plan the excavation with the same care you would give any other trench, and keep workers out of the zone as well as the machine.

Services and excavation near trees

Roots and services share the same ground, and a trench for a new water line, sewer or power connection can cut through roots that the arborist was trying to protect. Before any excavation near a tree, locate the underground services and confirm where they run. Before You Dig Australia provides a service for locating underground assets before digging, and that step should be taken before the first hole is dug, not after an unexpected pipe has been found.

Where a service must run through the root zone, agree the route with the arborist and the service provider before the trench is opened. Tunnelling or boring may avoid the root zone entirely, and that option is often cheaper than the damage to a mature tree. If the trench must be cut, the arborist may require root pruning under supervision, with clean cuts and immediate backfilling, rather than a rough cut by the machine.

Keep the trench open for as short a time as possible, and keep the spoil away from the roots. A trench left open over a weekend in wet weather can drain roots of oxygen, and a sudden rain can wash fine material into the root zone. Treat a trench near a tree as a short job, and plan the sequence so that the cut is made, the service is laid and the trench is closed without a long gap.

When removal needs approval

Removing a tree is a different matter from protecting one. Removal may be covered by the development consent, by a permit from the council, or by a specific provision for trees that are dangerous. The answer depends on the tree, its location and the approval that applies to the site, and it is the builder’s job to confirm which one applies before any work is done. Do not assume that a tree is exempt because it is in the way of the new house, or because the neighbour has asked for it to be removed.

Where the consent already allows removal of a named tree, keep a copy of that condition with the job file, and make sure the removal is carried out in the way the condition describes. Where the consent does not allow removal, the builder needs to seek approval before any work starts, and that may mean a variation to the consent or a separate permit. The article on development consent variations covers how changes to an approved project are handled.

Some work on trees may be exempt from the usual approval process, in some cases where a tree is dangerous. Any exemption is narrow and has to be checked against the current rules, and it is not a shortcut around the approval. If you believe a tree is dangerous, get it assessed by a qualified arborist, document the assessment and speak to the council before removing anything. A tree that is removed on the strength of a verbal assurance can turn into an unauthorised removal the moment the council sees it. The article on exempt development is a useful reference for the limits of what can be skipped.

Worked example: a tree on the boundary of a Sydney suburban block

Consider a builder in a Sydney suburb who was building a double-storey addition on a block with a mature tree close to the rear boundary. The tree overhung the neighbour’s yard, and the approval listed it as a tree to be retained. The builder’s first plan put the new footings close to the trunk, and the excavation crew cut into the root zone on the first day. The machine operator did not know the zone had been marked, and the fence had been moved to make room for a skip.

The builder found the damage a week later, when the crew noticed that the soil near the trunk had been cut back and the root zone was exposed. They stopped work, called the arborist, and called the certifier to report the breach. The arborist assessed the damage, recommended a changed footing design away from the trunk, and set out a monitoring plan for the tree over the following months. The neighbour was told what had happened in writing, and the builder agreed to cover the costs of the arborist’s assessment and the monitoring.

The tree survived, but it lost a significant part of its root system, and the builder spent more on redesigning the footings and monitoring the tree than the protection fence would have cost in the first place. The lesson was not that the crew was careless. It was that the protection zone was not part of the start-of-job briefing, and the fence was treated as a suggestion rather than a control.

The mistake that costs the most

Who to involve, and what to write down

A tree protection plan does not need to be long, but it does need to exist before the work starts. It should identify each protected tree, set the zone around it, state the fencing and signage, name the arborist who will assess any work inside the zone, and say who on the crew is responsible for checking the fence. Attach it to the job file and brief every subcontractor who will work near the tree, including the machine operators and the plumber.

The certifier, the council and the neighbour are the people who most often need to know what happened. Keep them informed in writing about any change to the plan, any damage to a tree and any approval that is sought or granted. A short note at the time is far better than an explanation given months later, when the detail has been forgotten and the tree has declined.

The guidance on protecting trees is a specialist field, and the arborist is the person to lead it. The builder’s role is to make sure the arborist’s advice is built into the program and the site, and that the crew follows it when the machine is running and the pressure is high.

Where tree work sits in the wider compliance picture

Tree protection is one part of a wider set of compliance duties that a licensed builder carries on a residential site. It sits alongside the consent conditions, the certifier’s inspections and the excavation controls, and it is easy to lose in the middle of a busy program. Make it a standing item on the pre-start checklist, and review it each time the site layout changes.

If you want to keep your licence and your knowledge current, the PointCPD guide to NSW builder CPD explains the renewal requirement and the topics that count. Site compliance topics like this one are the kind of practical learning that makes a builder more reliable on a difficult site.

Questions builders ask

• Approvals
• NSW Compliance
• Site Management

Published 12 October 2026. General information for builders, not legal, financial or engineering advice for a specific job. Check current requirements with the relevant regulator or standard before relying on them.