AS 4970:2025 Protection of trees on development sites replaced the 2009 edition on 30 May 2025. It introduces a Notional Root Zone, grades encroachment as minor, moderate, or major, and pairs a Tree Protection Plan drawing with written Tree Protection Specifications. Arborist reports for development should now cite the 2025 edition.
If you are lodging a development application with trees on or near the site, your arboricultural impact assessment needs to follow the current standard. This update explains what changed and why it matters to developers, builders, and councils.
What is AS 4970?
AS 4970 is the Australian Standard for protecting trees during development and construction. It sets out how an arborist identifies the trees to be retained, works out the area around each tree that needs protecting, assesses how much a design can encroach into that area, and specifies how the trees are protected during works.
Councils across NSW rely on AS 4970 when they assess development applications that affect trees. Many development control plans and lodgement guides refer to it directly.
What changed in AS 4970:2025?
Standards Australia published AS 4970:2025 on 30 May 2025. It supersedes AS 4970-2009, which had been in place for more than 15 years. An amendment, AS 4970:2025 Amd 1:2025, followed on 19 December 2025.
A Notional Root Zone
The 2025 edition introduces the Notional Root Zone (NRZ), a calculated root area for each tree. Encroachment into the NRZ is the starting point for deciding whether a design is acceptable and what further investigation is needed.
Three encroachment classes
The 2009 edition had two classes of encroachment, minor and major. The 2025 edition has three, minor, moderate, and major. Each class carries different expectations for justification and investigation. Higher levels of encroachment generally call for more evidence, such as root investigation, before an arborist can support the design.
The percentages that separate the classes are set out in the standard itself. We have not reproduced them here, because the standard is a copyright Standards Australia document and the detail matters when it is applied to a real tree.
Tree Protection Specifications and a Tree Protection Plan
The 2009 edition required a single tree protection plan. The 2025 edition pairs written Tree Protection Specifications (TPS) with a Tree Protection Plan (TPP) drawing. The specifications describe the protection measures and how they are to be maintained. The plan shows where those measures sit on the site.
The standard also describes a staged process that starts with a Preliminary Arboricultural Report and moves to an Arboricultural Impact Assessment once the design is known.
What are the Tree Protection Zone and Structural Root Zone?
The Tree Protection Zone (TPZ) is the area around a retained tree where construction activity is restricted, so that the roots and canopy needed for the tree to stay healthy are protected. It is usually marked out with fencing during works.
The Structural Root Zone (SRZ) is a smaller area closer to the trunk. It holds the roots that keep the tree upright. Encroaching into the SRZ puts the stability of the tree at risk, so it is treated with much more caution than the rest of the TPZ.
Both zones are calculated from measurements of the tree. The standard sets out the method, and the project arborist applies it to each tree on the site.
Why do reports citing the 2009 edition draw council queries?
Councils are now asking for reports prepared under the 2025 edition. For example, Inner West Council’s development application lodgement guide states that an arboricultural impact assessment must be prepared in accordance with AS 4970:2025. Waverley Council asks for retained trees to be protected in accordance with the 2025 standard.
A report that cites AS 4970-2009 will not use the Notional Root Zone, the three encroachment classes, or the new specification and plan format. A council assessor may then ask for more information or an updated report, which can add weeks to an assessment.
What this means for your project
For a new development application, ask for the arborist report to be prepared under AS 4970:2025 and to say so. Check that it includes Tree Protection Specifications and a Tree Protection Plan, not only a general plan.
For a project already approved under a report citing the 2009 edition, the approved conditions generally still govern the works. If you are lodging a modification or a new application on the same site, expect the council to ask for the current standard.
During construction, the protection measures still need someone to check them. A project arborist can inspect fencing and works near retained trees and certify compliance at the stages the consent requires. Our arboriculture services cover each stage.
Frequently asked questions
Does my council accept AS 4970:2025 now?
Yes. AS 4970:2025 has been the current standard since 30 May 2025, and councils are already requiring it in lodgement guides and tree pages. Some development control plans still refer to the 2009 edition by name. Where that happens, the council will usually expect the current standard, but it is worth confirming with the assessing officer.
What is a Tree Protection Zone?
A Tree Protection Zone is the area around a retained tree where construction activity is restricted, to protect the roots and canopy the tree needs to survive. It is calculated from the size of the tree and usually fenced during works. Encroachment into it has to be assessed and justified by an arborist.
Do existing arborist reports need updating?
For an application already approved, generally not, because the consent conditions govern the works. For a new application or a modification, a report that cites AS 4970-2009 is likely to draw a request for information. Updating the report before lodgement is usually quicker than responding to a council query later.
Sources
- Standards Australia, AS 4970:2025 Protection of trees on development sites
- Standards Australia, AS 4970:2025 Amd 1:2025
- Inner West Council, DA Lodgement Guide for Applicants
- Waverley Council, Trees and development
Related projects: arboricultural impact assessment at Norwest and Richards Precinct, Riverstone West.
Related updates: What changed in the Biodiversity Offsets Scheme on 7 March 2025.
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