Arborist report (DA submission)
Arborist report is a qualified arborist's DA-submission assessment of trees on or adjoining a site: health, structure, retention value, impact, TPZ design.
Ask Chalkline about this →An arborist report is the qualified arborist’s written assessment of trees on or adjoining a development site, submitted with a development application to demonstrate that the proposed works comply with the council’s tree management policy and AS 4970:2009 (Protection of trees on development sites). The report addresses each significant tree’s health, structural integrity, retention value, and the specific impact of the proposed building work within the Tree Protection Zone (TPZ) of each tree. Most NSW and Victorian councils require an arborist report for any DA that affects trees over a specified trunk diameter (typically 15-30 cm DBH) or that involves listed protected species. Verified per AS 4970:2009 and standard council DCP requirements (2026-05-16).
The arborist’s standard categories of assessment:
| Category | What it assesses |
|---|---|
| Tree identification | Botanical name, common name, age estimate |
| Tree dimensions | DBH (diameter at breast height), crown spread, height |
| Tree health | Visual tree assessment (VTA); decay, disease, vigour |
| Tree structure | Crown structure, included bark, decay cavity, lean |
| Retention value | Aesthetic, ecological, cultural value; visual significance |
| Useful Life Expectancy (ULE) | Forecast remaining life: <10y, 10-20y, 20-40y, >40y |
| TPZ radius | Calculated per AS 4970 (12x DBH for healthy trees, larger for protected species) |
| Construction impact | Description of proposed works within or near the TPZ |
| Recommendations | Retain, remove, replace, transplant, modify the design |
The Tree Protection Zone (TPZ):
The TPZ is the cylindrical zone around a tree where construction activities are restricted to protect roots and trunk. AS 4970 specifies:
| Tree size | TPZ radius |
|---|---|
| DBH < 15 cm | Often exempt |
| DBH 15-50 cm | 12 x DBH (e.g. 25 cm DBH → 3.0 m radius) |
| DBH 50-100 cm | 12 x DBH minimum, up to 15 m maximum |
| DBH > 100 cm | 12 x DBH up to 15 m maximum, depending on species |
Within the TPZ:
- No structural excavation (foundations, services trenching, retaining walls).
- No vehicle access without temporary protective panels.
- No stockpiling of materials.
- Tree protection fencing at the TPZ perimeter throughout construction.
Common impact scenarios:
| Proposed work | Arborist response |
|---|---|
| Slab edge within TPZ | Recommend redesign; if unavoidable, manual hand-dig footings with arborist supervision |
| New driveway within TPZ | Recommend permeable surface (gravel, pervious concrete) over root zone |
| Tree removal proposed | Provide retention vs removal analysis; council-mandated replacement planting |
| Pruning required | Specify scope per AS 4373 (Pruning of amenity trees); supervised by arborist |
| Footings adjacent to TPZ | Pier-and-beam recommended; minimal excavation; supervised by arborist |
| Construction access path | Specify temporary protective panels or boardwalk over TPZ |
Qualifications expected:
| Level | Typical credential |
|---|---|
| Consulting arborist | Diploma in Arboriculture (AQF Level 5) + extensive site assessment experience |
| Member of professional body | International Society of Arboriculture (ISA), Arboriculture Australia |
| Council-approved arborist | Some councils maintain panels of approved consulting arborists |
Typical arborist report fees (residential):
| Scope | Fee (ex-GST) |
|---|---|
| Single tree assessment | $400-$800 |
| Multiple trees (5-10) | $1,500-$3,000 |
| Major site with multiple trees + heritage | $4,000-$8,000 |
| Court appearance / expert witness | $400-$1,500/hour |
When an arborist report is required:
| Trigger | Application |
|---|---|
| DA on a lot with trees over 15-30 cm DBH (council-specific) | Standard residential DA in NSW and Vic |
| Heritage item with significant trees | Almost always required |
| Bushland or environmentally-sensitive zone | Required |
| State-significant trees | Required, plus separate state heritage approvals |
| Removal of any protected species | Required, plus specific permit |
| Subdivision touching trees | Required for the subdivision approval |
Common defects in arborist reports:
- Outdated assessment: a 2-year-old report on a tree that has since deteriorated; rejection or info request.
- Generic recommendations: “tree should be retained” without proposed methodology to achieve retention.
- Missing TPZ calculation: report identifies the tree but doesn’t define the protection radius.
- No drawings: written description only; council requires drawings showing the building footprint, TPZ, fencing.
- Arborist not qualified: assessment by a non-qualified person (e.g. landscape architect alone); rejection.
- Underestimating tree retention value: minimising significance to support removal; council disputes and engages independent arborist.
Builder takeaway:
- For sites with significant trees, brief the arborist before finalising the design; tree protection often drives footprint and access decisions.
- Bring the arborist into the design coordination meeting alongside the architect and engineer.
- Document arborist recommendations into the building program; tree protection fencing must be in place before any excavation.
- Engage the arborist for construction-stage supervision (typically monthly site visits) on sensitive sites; arborist sign-off at completion.
Also known as: consulting arborist report; tree assessment report; tree report; AS 4970 report; arboricultural impact assessment (AIA).
Category: Approvals & DA.
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Last updated: 2026-05-16. Verified: 2026-05-16. Quarterly review for currency.