Answer first: Most Greater Sydney councils will ask for an Arboricultural Impact Assessment (AIA) where a Development Application affects the Notional Root Zone (NRZ) of protected onsite trees, neighbouring trees or street trees. Engage an AQF Level 5 consulting arborist early, design to AS 4970:2025, and lodge a site-specific AIA with Tree Protection Plan and Specifications — generic reports attract RFIs.
Author: Franz Phan, Senior Planning Consultant, giantA Pty Ltd · Updated 17 September 2026
When do NSW councils require an arborist report with a DA?
Trees are not a side issue on NSW Development Applications. The Planning Secretary’s Application requirements already require a site plan to show existing vegetation and trees, and drawings to show proposed landscaping. Where those trees are prescribed (protected) under a council Development Control Plan, or where works encroach into root or canopy zones of onsite, adjoining or public trees, councils commonly elevate the documentation to a formal arboricultural report prepared by a consulting arborist.
In practice, Greater Sydney assessing officers ask for arborist material when any of the following apply:
- works (building footprint, excavation, services, driveways, OSD, scaffolding or construction access) will enter the NRZ of a prescribed tree
- street trees or neighbour trees could be affected by demolition, excavation or canopy clearance
- the proposal seeks removal of a prescribed tree and needs retention-value justification
- the landscape or deep-soil strategy depends on retaining canopy for LEP/DCP compliance
Sources: NSW Application requirements (PDF) · Inner West — Documentation requirements · North Sydney — Trees in Development Applications.
Related giantA pathway reading: DA & CDC Checklist NSW 2026 · CDC vs DA Approval NSW · Specifications required for DA lodgement · NSW tree removal and vegetation clearing laws 2026.
What changed under AS 4970:2025 for tree protection on development sites?
On 30 May 2025, Standards Australia published AS 4970:2025 Protection of trees on development sites, superseding AS 4970-2009. Greater Sydney councils — including Inner West and North Sydney — now expressly require AIAs and Tree Protection Plans to be prepared in accordance with the 2025 standard.
The terminology shift that most architects and owners need to understand is this:
- Notional Root Zone (NRZ) — the calculated theoretical area set aside for roots needed for stability and ongoing health. Inner West describes the NRZ as a notional circular area with a specified radius from the trunk centre, determined using the methodology in AS 4970:2025.
- Tree Protection Zone (TPZ) — under the updated standard, TPZ refers to the area that is actually protected on site during construction (fencing, ground protection and controls), not merely the theoretical circle on a plan.
- Structural Root Zone (SRZ) — the critical root area for stability; intrusion into the SRZ is treated as a major impact.
- Diameter at Standard Height (DSH) — the measurement used in the updated standard’s root-zone methodology (replacing older “DBH” language in many report templates).
North Sydney’s published AIA guidance quantifies NRZ encroachment categories as:
- Minor: ≤10% NRZ and outside the SRZ
- Moderate: greater than 10% and ≤20% NRZ, and outside the SRZ
- Major: NRZ encroachment greater than 20%, or any work inside the SRZ
Those percentages drive whether a design tweak, root mapping, or a redesign is needed before lodgement. Do not treat a 2009-era “10% TPZ is always fine” note as current practice.
Sources: Standards Australia AS 4970:2025 (published 30 May 2025) · North Sydney AIA encroachment categories · Inner West AIA / AS 4970:2025 requirement.
What is the difference between a Preliminary Tree Assessment and an AIA?
Councils distinguish early design advice from lodgement-grade impact assessment.
Preliminary Tree Assessment (PTA) — typically prepared after survey, early in concept design. It identifies trees on the site and neighbouring / public trees whose NRZ may be affected, assigns retention values, and guides the architect toward a footprint that can actually retain high-value canopy. Inner West notes a PTA is highly recommended for sites with prescribed trees, even where it is not lodged with the DA.
Arboricultural Impact Assessment (AIA) — prepared once the development design is sufficiently final. North Sydney requires an AIA where works will occur in the NRZ of one or more trees. Inner West requires an AIA when development will directly or indirectly impact the NRZ of prescribed trees on the site and trees on adjacent sites (including street trees).
Skipping the PTA and jumping straight to a late AIA is how projects discover — after the architecture is locked — that a driveway, basement ramp or service trench sterilises the very trees the DCP expected you to keep.
| Document | When it is used | What council is checking |
|---|---|---|
| Preliminary Tree Assessment | Concept / sketch design | Which trees have retention value and which NRZs constrain the footprint |
| Arboricultural Impact Assessment (AIA) | DA lodgement (final design) | Quantified NRZ/SRZ/TPZ impacts, removals justification, mitigation |
| Tree Protection Plan (TPP) + Specifications (TPS) | DA and then construction | Fencing, ground protection, monitoring and certification under AS 4970:2025 |
| Root Mapping Report | Where viability is uncertain | Location/size of significant roots via non-destructive investigation |
| Pruning Specification | Where canopy clearance is needed | AS 4373 pruning extent, photos and % canopy loss |
What must a council-ready AIA include?
Generic “the trees will be fine” letters are rejected. Inner West states that reports must be site-specific, evidence-based and impartial; reports older than 12 months are generally not accepted. North Sydney publishes a detailed report layout that aligns with AS 4970:2025.
A strong AIA package typically includes:
- Arborist credentials — AQF Level 5 (Diploma of Arboriculture) or equivalent; contact details and independence statement.
- Plans assessed — architectural, survey, landscape and engineering versions with dates/revision numbers.
- Tree schedule — unique IDs, scientific/common names, dimensions, health/structure, ULE, retention value, NRZ, SRZ, TPZ and encroachment %.
- Scaled tree plan — trees to retain / remove / transplant; NRZ/SRZ/TPZ overlays; services, levels and construction access.
- Impact discussion — demolition, excavation, stormwater, scaffolding, crane/piling clearances, landscaping and neighbour/street trees.
- Encroachment classification — minor / moderate / major with mitigation methods.
- TPP and TPS — fencing, ground protection, root protection, monitoring stages and certification.
- Replacement planting — species, size and quality where removals are justified.
Sources: North Sydney — AIA / TPP / TPS content · Inner West — AIA checklist guidance.
How do NRZ encroachment categories change design decisions?
Encroachment is not just a spreadsheet cell — it is a design brief.
- Minor (≤10%, outside SRZ): usually manageable with standard tree protection during construction, provided there are no cumulative recent encroachments. Still show the numbers and the TPP.
- Moderate (>10% to ≤20%, outside SRZ): expect the project arborist to demonstrate viability with tree-sensitive construction methods (hand dig / hydro-vac for services, pier-and-beam, suspended slabs, relocated trenches) and a clear TPS.
- Major (>20% or any SRZ intrusion): redesign is often cheaper than arguing. Where retention is still proposed, councils commonly expect non-destructive root mapping and a detailed viability argument. Inner West notes root mapping is likely where other assessments are unclear, and generally where proposed development involves greater than 10% NRZ encroachment.
For architects, the highest-yield coordination habits are: freeze survey tree numbers before sketch design; keep service routes and OSD tanks out of high-value NRZs; and bring the arborist into the same coordination meeting as the civil engineer — not after the stormwater concept is already lodged.
How do DA tree reports relate to SEPP vegetation clearing rules?
Do not confuse a DA-linked tree assessment with a standalone vegetation clearing permit.
Chapter 2 (Vegetation in non-rural areas) of the State Environmental Planning Policy (Biodiversity and Conservation) 2021 regulates clearing that is not linked to development requiring consent. Clearing that is ancillary to a DA is assessed as part of that development assessment process (and may also engage the Biodiversity Conservation Act 2016 where thresholds are met). Heritage trees / trees in heritage conservation areas generally need development consent under the LEP pathway.
Separately, many councils still run tree permit systems under their DCP for works that are not part of a DA. If your project is already on the DA pathway, put the tree impacts inside the DA package (AIA + SEE synthesis) rather than assuming a later tree permit will “sort it out”.
Sources: NSW Planning — Vegetation in non-rural areas · Chapter 2 SEPP FAQ for councils (PDF).
For the broader statewide vegetation / NVR mapping context, see giantA’s tree removal and vegetation clearing guide.
What belongs in the SEE versus the arborist package?
The Statement of Environmental Effects remains the integrating planning narrative. The AIA proves the technical tree conclusions. A common RFI pattern is a thin SEE that says “see arborist report” with no synthesis — or an AIA that assesses an outdated architectural revision.
- Keep in the SEE: why trees matter for streetscape/character and DCP landscaped area / deep soil; a short summary of retain vs remove; cross-reference to the AIA PDF; and how construction impacts will be managed.
- Keep in the AIA / TPP / TPS: NRZ maths, encroachment %, species data, protection fencing details, root mapping method and monitoring hold-points.
- Match the drawings: every tree number on the AIA plan must match the survey and the landscape plan lodged on the NSW Planning Portal.
Related giantA reading: Statement of Environmental Effects NSW DA 2026 · Pre-DA meetings NSW 2026.
How should architects and owners brief an AQF Level 5 arborist?
Both Inner West and North Sydney expect AQF Level 5 consulting arborists for AIA work. Brief them with a pack that prevents redraws:
- current feature & level survey with tree trunks accurately located
- architectural DA set (site, floor, elevations, sections) plus civil/stormwater concept
- known construction method (slab, pier, basement, crane locations)
- Section 10.7 certificate and any heritage / biodiversity notations
- photos of street trees and neighbour canopy near boundaries
- clear design priorities — which trees the client is willing to redesign around
At giantA, we treat tree retention as a design constraint from sketch design, not a Portal afterthought. If the architecture is still moving weekly, freeze a “tree revision base” set so the AIA encroachment table is not chasing moving walls.
Frequently asked questions
Do all NSW residential DAs need an arborist report?
No. Many simple alterations with no prescribed trees and no NRZ encroachment do not. Where prescribed trees, street trees or neighbour trees are affected — or where the DCP checklist lists an AIA — expect to lodge one. Always check your council’s tree DCP / lodgement checklist before assuming exemption.
Who can prepare an AIA for Greater Sydney councils?
Inner West and North Sydney require an arborist with AQF Level 5 in Arboriculture (or equivalent). Using an under-qualified report is a common reason for rejection or RFI.
Is AS 4970-2009 still acceptable in 2026?
AS 4970:2025 superseded the 2009 standard on 30 May 2025. Councils that cite the 2025 standard (including Inner West and North Sydney) expect current methodology, NRZ language and encroachment categories. Confirm the version named in your council’s checklist.
What if we only need to prune for crane or scaffolding clearance?
Expect a pruning specification consistent with AS 4373 and the tree protection standard, with photos and calculated canopy loss. Significant habitat hollows may also need ecological advice under the Biodiversity Conservation Act 2016.
When is root mapping required?
When viability after encroachment is uncertain — commonly for major NRZ impacts or SRZ risk. Inner West generally expects root mapping where proposed development involves greater than 10% NRZ encroachment and other assessments are not clear. Use non-destructive methods (hand dig / air excavation), not destructive machinery.
How does this interact with CDC vs DA?
Complying Development has its own Codes SEPP constraints; many tree-sensitive sites fall out of CDC and into DA. Resolve the pathway early using giantA’s CDC vs DA guide before commissioning a full AIA for the wrong approval track.
How giantA coordinates tree-ready DA packages
giantA Pty Ltd provides architectural and drafting services with BASIX/NatHERS coordination for projects across Parramatta CBD and Greater NSW. We coordinate survey, architecture, civil and consulting arborists so NRZ constraints inform the footprint before Portal lodgement — reducing RFIs that stop the assessment clock. Start with our specifications required and DA/CDC checklist pages, or talk to the team at giantA.com.au.