PAR vs AIA — Which Arborist Report Do You Need?
Trees on or near your project? Free 5-question wizard tells you whether you need a Preliminary Arboricultural Report (PAR), Arboricultural Impact Assessment (AIA), Tree Protection Plan (TPP), expert witness report — or nothing at all. Built for NSW DA workflows.
Tip: council generally requires assessment of any tree whose Tree Protection Zone (TPZ) overlaps the works — even neighbour or street trees.
Answer all 5 questions then click Show recommendation. The result panel appears on the right (or below, on mobile).
Disclaimer & conditions of use
Purpose. This tool helps you identify the most likely arborist-report category for a NSW project at a given stage. It is provided for triage and education only.
Not a council determination. The recommendation is based on common NSW DCP and AS 4970-2025 practice. The specific report your council will accept depends on the local Development Control Plan (DCP), Tree Preservation Order or Vegetation SEPP, the consent authority’s pre-DA advice, and any conditions imposed during the DA process. Always verify the report type with your council’s pre-DA service before commissioning work.
Cost & timing are indicative. Quoted ranges are typical for Assurance Trees Pty Ltd as at 2026 and depend on site complexity, tree count, access, and the level of detail your council requires. Final quotes are issued after a brief site brief and aerial review.
Inputs. Output reflects the answers given. If site conditions, council requirements or design status change, the appropriate report type may change. Re-run the tool if any key answer changes.
Not legal or planning advice. This tool does not constitute legal, planning, engineering or arboricultural advice in respect of a specific site. Engage qualified professionals for site-specific recommendations.
No warranty, no liability. Provided “as is” without warranty of any kind. To the maximum extent permitted by law, Assurance Trees Pty Ltd accepts no liability for any loss, additional cost, or delay arising from use of or reliance on this tool.
Need help deciding? Call Assurance Trees on 1300 859 510 or email sales@assurancetrees.com.au. We’ll look at your site and council brief and confirm the right scope before quoting.
Need the actual report?
Assurance Trees writes PARs, AIAs, TPPs and expert reports to AS 4970-2025 across NSW. 15+ years of consulting, AQF Level 5, in-house GIS and air spade root investigation. See our AIA service · See our PAR service · call 1300 859 510.
The four arborist-report categories explained
NSW Development Applications, construction certificates, and dispute matters use a small set of arboricultural reports. Picking the right one depends on when in the project you are and why you need it.
Preliminary Arboricultural Report
The early-stage report. Identifies trees on and near the site, their species, height, dimensions, retention value and constraint footprint (TPZ / SRZ from AS 4970-2025). Used to inform design before the building footprint is locked in. The cheapest and fastest report — and the one that saves the most money later.
When: due diligence, site purchase, concept & early design.
Cost: typically $1,500–$2,500 + GST
Turnaround: 5–7 business days.
Arboricultural Impact Assessment
The DA-stage report. Takes the design layout and quantifies impact on each retained tree — encroachment percentage into TPZ / SRZ classified as Minor / Moderate / Major per AS 4970-2025, mitigations (air spade investigation, hand excavation, root pruning protocol), replacement plantings, and tree-protection specifications. Required by most NSW councils for any DA that affects trees.
When: design 80%+ complete / DA submission.
Cost: typically $1,800–$3,500 + GST.
Turnaround: 7–14 business days.
Tree Protection Plan
The construction-stage report. A drawn site plan with TPZ fencing, ground protection, signage, supervision and reporting requirements. Usually a deliverable of the AIA, but can be commissioned as a standalone when a DA was approved without one and council has now made it a pre-construction condition.
When: post-DA, pre-construction.
Cost: typically $1,200–$2,500 + GST standalone.
Turnaround: 5–10 business days.
Expert Witness / Specialist Report
For matters outside the DA pathway: insurance claims, boundary disputes, alleged tree damage, court / tribunal proceedings, post-failure investigation. Includes site-specific evidence, photographic record, comparative analysis, and (when needed) sworn statement compliant with the relevant court’s Expert Witness Code of Conduct.
When: disputes, insurance, court / tribunal.
Cost: from $2,500 + GST, scoped per matter.
Turnaround: depends on matter urgency.
Common mistake. Commissioning an AIA before the design is locked in. If the building footprint shifts (a common outcome of a PAR), the AIA has to be redone — you pay twice. For greenfield sites, sites with multiple significant trees, or any project where the design is still flexible, do the PAR first.
Side-by-side comparison
| PAR | AIA | TPP | Expert | |
|---|---|---|---|---|
| Project stage | Pre-design / concept | Design ~80%+ / DA | Post-DA / pre-build | Any (dispute) |
| Used for | Constraint mapping, design input | DA submission, council acceptance | Construction supervision | Insurance, court, dispute |
| Includes design impact? | No — identifies trees only | Yes — TPZ encroachment per tree | Yes — fencing & protection | Site-specific scope |
| Includes replacement schedule? | No (high-level only) | Yes — council-ready | No | If relevant to matter |
| AS 4970-2025 calculations? | Tree-level dimensions only | Yes — full encroachment classification | References AIA outputs | If relevant |
| Indicative cost (NSW) | $1,500–$2,500 | $1,800–$3,500 | $1,200–$2,500 | From $2,500 |
| Turnaround | 5–7 days | 7–14 days | 5–10 days | Scoped |
| Council acceptable for DA? | Only as pre-DA | Yes — primary DA document | Usually condition-of-approval | N/A |
Frequently asked questions
Can I skip the PAR and go straight to AIA?
Yes — if your design is locked in and you’re ready to lodge a DA, the AIA is the right report. Skip the PAR when there are few trees, the design has no flexibility, or the trees are clearly outside the footprint. The PAR pays for itself when there are multiple trees or significant trees, or when the design can still shift to retain a more valuable tree.
My council never asked for an arborist report — do I still need one?
If your works are within the Tree Protection Zone (TPZ) of any tree on the site, neighbouring property, or street verge, council usually requires assessment under the local DCP, the Tree Preservation Order, or NSW BDAR / SEPP Biodiversity. The safest path is a pre-DA enquiry asking the question directly. The cost of finding out at the RFI stage (Request for Information — council asks for more documents mid-DA) is weeks of delay.
What does AS 4970-2025 actually require?
AS 4970-2025 (formerly 4970-2009) is the Australian Standard for Protection of Trees on Development Sites. It defines how to calculate the Tree Protection Zone (TPZ) and Structural Root Zone (SRZ) from trunk diameter, classifies encroachment as Minor (≤10%), Moderate (>10–20%) or Major (>20% or any SRZ encroachment), and prescribes air spade investigation, hand excavation, and root pruning protocols for impacted trees. A council-accepted AIA references the standard throughout.
The street tree is council’s — do I still have to assess it?
Yes. AS 4970-2025 protects any tree whose TPZ encroaches on the proposed works — including neighbour trees and street trees. Most NSW councils require the AIA to identify and protect adjacent and street trees, with the same encroachment classification and protection measures. Damage to council street trees during construction can attract significant fines and replacement orders.
Can the PAR and AIA be combined into one report?
For very small sites — one or two trees, simple design — yes, the PAR and AIA can be merged. For anything larger, the value of the PAR is in informing the design phase, so combining them defeats the point. Most projects benefit from staging: PAR first (inform design), AIA at DA (assess impact of locked design).
What happens if my AIA shows Major encroachment?
Major encroachment (>20% of TPZ, or any SRZ encroachment) triggers mandatory air spade investigation under AS 4970-2025. The investigation maps the actual root layout in the impact zone so the design can shift, mitigate, or in the worst case justify removal with appropriate replacement. Assurance Trees has in-house air spade equipment, so we can deliver investigation, AIA and design-revision conversation in one site visit.
How long is an AIA valid for?
Most NSW councils accept an AIA for 12–24 months from the date of inspection, provided site conditions don’t materially change. If the DA process drags on, council may ask for an updated inspection. The tree dimensions, the AS 4970-2025 calculations and the proposed protection methodology don’t typically change — the inspection date is what gets refreshed.
What if I’m in a dispute with my neighbour about a tree?
That’s an Expert Witness matter, not a DA report. Neighbour tree disputes in NSW are usually heard in NSW LEC (Land & Environment Court) under the Trees (Disputes Between Neighbours) Act 2006. Expert reports must comply with the Expert Witness Code of Conduct (UCPR Schedule 7). Assurance Trees writes code-compliant expert reports and has appeared in LEC matters.
Definitions — key terms
Terms used on this page, drawn from AS 4970-2025 and NSW DA practice.
- PAR — Preliminary Arboricultural Report
- An early-stage report identifying trees on and adjacent to a site, their species, dimensions, retention value and constraint footprint. Used to inform design before a building layout is locked in. Not normally accepted as the DA-stage arborist report.
- AIA — Arboricultural Impact Assessment
- The DA-stage arborist report. Takes a fixed design and quantifies impact on each retained tree per AS 4970-2025: TPZ / SRZ calculation, encroachment classification, mitigation protocols, replacement schedule, and tree-protection specifications.
- TPP — Tree Protection Plan
- A drawn plan showing TPZ fencing, ground protection, signage and construction-stage supervision requirements. Usually a deliverable of the AIA; can be commissioned standalone as a condition of approval.
- TPZ — Tree Protection Zone
- In AS 4970-2025 the TPZ is the physical fenced area on site that protects the tree during construction. The calculation that defines its dimensions is the Nominal Root Zone (NRZ).
- NRZ — Nominal Root Zone
- The calculation in AS 4970-2025 (radius = DBH × 12) that defines the area within which roots are expected. Sets the radius of the TPZ. (In the 2009 edition this calculation was itself called the TPZ.)
- SRZ — Structural Root Zone
- The smaller zone within the NRZ containing the woody buttress roots that hold the tree up. Encroachment here is treated as Major impact regardless of percentage.
- DBH — Diameter at Breast Height
- The diameter of the trunk measured at 1.4 m above ground level. Used to calculate the NRZ / TPZ radius.
- Encroachment classification
- AS 4970-2025 classifies impact on each retained tree by the percentage of TPZ encroached: Minor (≤10%), Moderate (>10–20%) or Major (>20% or any SRZ encroachment). Each tier triggers progressively more rigorous mitigations.
- Air spade investigation
- A non-destructive method of exposing roots using compressed air. Required under AS 4970-2025 in Moderate or Major encroachment to map the actual root architecture before final mitigation is selected. Assurance Trees has in-house air spade capability.
- DCP — Development Control Plan
- The council’s local planning document that sits under the LEP. NSW DCPs commonly require an arborist report when development affects trees of a defined size or value.
- RFI — Request for Information
- A council request mid-DA for additional documents or clarification. A common cause of weeks of delay; commonly triggered by an inadequate or missing arborist report.
- Expert Witness Code of Conduct
- NSW Uniform Civil Procedure Rules Schedule 7 — the conduct and content rules an expert report must meet to be admissible in NSW courts and tribunals, including the NSW Land & Environment Court.
Ready to commission your arborist report?
Assurance Trees writes PARs, AIAs, TPPs and expert reports to AS 4970-2025 across NSW. 15+ years consulting, AQF Level 5, in-house GIS & air spade. Quote in 24 hours.
1300 859 510or email sales@assurancetrees.com.au
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