Trees need to be considered early in the design process so that the highest value site trees can be viably retained where possible. While a Preliminary Tree Assessment is not required to be submitted to Council, it is highly recommended for sites with prescribed (protected) trees, to assist in identifying the retention value of the trees and provide guidance on achieving development aspirations for a particular site.
One or more of the following reports may be required with an application:
• Arboricultural Impact Assessment (AIA) Report
• Tree Protection Plan and Specification
• Tree Assessment and Pruning Specification
• Root Mapping Report
• Tree Risk Assessment Report
• Structural Engineering Report
• Plumbing Report
Reports must be specific to a site and must address the specifics of the project, in detail. Generic reports will not be accepted.
All reports must be evidence-based and impartial. Unsubstantiated opinions will not be accepted or considered in the assessment of the proposal. The reports must relate to the tree/s as they exist at the time of the submission of the application to Council. Reports that are more than 12 months old will generally not be accepted.
Subject matter experts will review all reports submitted and consider the appropriateness of the level of detail, and relevance of information provided. Council may require additional information or may not agree with the findings or recommendations in a report.
Reports must be submitted with the relevant checklist, completed.
An AIA is required when the development of a site will directly or indirectly impact the Notional Root Zone (NRZ) of prescribed trees within the site and all trees on adjacent sites (including street trees).
The report must be prepared in accordance with Australian Standard AS 4970:2025 Protection of trees on development sites noting the standard includes the methodology for determining the NRZ The NRZ is the area set aside for the protection of the roots required for the stability and ongoing health and viability of the tree. The NRZ is a notional circular area with a specified radius from the centre of the trunk.
All large shrubs and trees on adjacent sites (whether prescribed or not) must be considered in the design to ensure that the proposed development will not result in impacts that will reduce the structural stability or ongoing health of the vegetation.
The AIA report must include an accurate and comprehensive assessment of the likely impact of the proposed development on the trees to be retained where the development will encroach into the NRZ and canopy of those trees. This must also include assessment of associated works such as demolition, service installation, stormwater management, construction access routes, site storage, piling, rigging, internal power poles, landscaping, scaffolding etc.
Discussion and recommendations are required as part of the AIA, relating to design modifications and construction methods to minimise the impact on trees to be retained. Where the submitted plans do not reflect the recommendations, Council may ask for amended plans prior to the application being determined.
Note: Where pruning of a tree canopy is required, a detailed specification must be included. Refer to Pruning Specifications. Generally, site and project specific Tree Protection Plans and specifications are required within the AIA report. A root mapping report is likely to be required if other assessments of the impact of the proposal are not clear or certain. (Refer also to Tree Protection Plans and Specifications and Root Mapping reports).
Download the Checklist - Arboricultural Impact Assessment (PDF, 143.61KB)
Council will require project-specific tree protection measures to be provided for all trees on a development site (and any trees on adjoining private or public land if the proposed development will encroach into the TPZ of those trees). The protection measures must comply with AS 4970:2025 Protection of trees on development sites.
The plan must detail all proposed measures for the protection of trees throughout the entire development and construction process, and may include tree protection measures associated with demolition, scaffolding, hoarding, excavation, clearance for use of piling rigs, cranes and tipper trucks, vehicular access routes, materials storage areas, as well as works that need to be directly supervised by an arborist.
Note: Where pruning of a tree crown is required for building or construction clearance, it must be shown on the tree protection plan, and a detailed specification must be included. (Refer also to Tree Assessment and Pruning Specification.)
A tree assessment and pruning specification is required if proposed tree work exceeds the exempt works set out in the Tree Management Development Control Plan, 2023.
Tree pruning (crown or roots) is likely to have an impact on the health and structural condition of a tree because it reduces the all-important foliage the tree uses to photosynthesize and alters its exposure to sun and wind loads. It may have a detrimental effect on a tree’s long-term viability.
Pruning of a tree’s canopy may impact habitat such as hollows. Trees likely to support habitat may need additional assessment by an ecologist or wildlife specialist in accordance with the Biodiversity Conservation Act 2016. Pruning may also change the tree’s contribution to the landscape amenity and therefore impact its landscape significance.
In some situations, a Pruning Specification prepared by and AQF Level 3 Arborist is sufficient.
Download the checklist - Tree Assessment & Pruning Spec (PDF, 141.24KB)
Root mapping involves the investigation and documentation of part of a tree’s root system and can provide useful information when proposed development is situated near trees, or when there's a suspicion of root-related damage to buildings or infrastructure.
Council may require root mapping to be undertaken, as part of a thorough assessment of the impact of proposed development on the tree’s root system, and therefore health and structural stability of the tree. Generally, root mapping is required when proposed development involves greater than 10% encroachment into the Notional Root Zone of a tree.
Investigation of the location of tree roots usually requires a trench to be excavated to a sufficient depth as indicated by Council or to the maximum depth at which tree roots are likely to grow given the soil type and site conditions (usually in the range of 500-800mm). All roots of greater than 15mm diameter should be preserved without damage during investigation.
The excavation can be carried out using minimally destructive methods such as hand digging or Air Spade ® (or similar) excavation. Potentially destructive machinery or tools such as mattocks and crow bars must not be used. Where techniques employing pressurised air or water are used, equipment must be carefully calibrated to ensure tree roots will not be damaged.
Root mapping reports provide detailed documentation of root mapping investigations, with graphic representation of the location and size of trenches as well as the location, size and depth of roots discovered therein.
Download the checklist - Root Mapping Report (PDF, 152.11KB)
A tree risk assessment report may be required when the applicant considers that a tree presents an unacceptable risk to people or property. The assessment must be carried out by a person who has a qualification in an industry recognised tree risk assessment methodology. Acceptable risk assessment systems are: Quantified Tree Risk Assessment (QTRA) Tree Risk Assessment Qualification (TRAQ) or VALID.
The report must identify the specific hazards associated with the tree as well as the likely targets, assess the likelihood of failure and document the reasoning for the categories/inputs selected and the assessed risk level. It must also recommend measures for managing risk.
Recommendations must be unambiguous, e.g.: the tree is calculated as being of high risk for life and property and is recommended for removal; the tree is considered to be of moderate risk for property and is recommended for retention, subject to the following risk reduction actions, etc.
Download the checklist - Tree Risk Assessment (PDF, 128.63KB)
A structural engineer’s report is required where the applicant considers that structural damage to a significant structure, such as a dwelling, has been caused by a tree. The assessment must be undertaken by a qualified Structural Engineer, and the report must demonstrate that the tree is directly causing or is contributing to the damage. Structural failures must not be attributed to a tree merely because the tree is growing nearby.
Cracking and other signs of damage in older buildings may be due to poor construction techniques or the age of the fabric. Fine cracks in cement render or plaster may occur in both old and new buildings and not necessarily indicate a structural fault. Large cracks (wider than 5mm in a structural supporting wall) may indicate movement in the foundation material such as the expansion and contraction of reactive clay soils.
If damage is attributed to tree roots, it must be shown that there is direct contact between woody roots and the structural fabric. This may require non-invasive, exploratory investigations in the form of root mapping. Refer to Root Mapping reports
The report should consider engineering solutions that allow the tree to be retained. Where appropriate, the structural engineer should liaise with a consulting arborist to assist in developing a strategy to retain or protect the tree.
A plumber’s report is required where it is claimed that damage to a plumbing system has occurred due to tree roots. Plumber’s reports must be prepared by plumbers who hold a current license issued by the NSW Office of Fair Trading. Reports prepared by an unlicensed plumber or reports that do not contain the minimum specified content will not be accepted. Council recommends that closed circuit television (CCTV) drain camera investigation also be carried out by a licensed plumber.
The evidence must show conclusively that significant damage has initially occurred as a direct result of the tree. The report is to include a discussion of alternative repair methods, including pipe modification, line redirection and relining or re-sleeving. Options for rectification works that may permit retention of the tree/s must be considered.