Arborist Reports Explained: What You Need to Know
Understand the different types of arborist reports, when you need one, what they cost, and how to choose the right qualified professional for your situation.
Get an Arborist Report QuoteWhat Is an Arborist Report?
An arborist report is a professional document prepared by a qualified consulting arborist that provides an expert assessment of one or more trees. The report evaluates the tree's health, structural integrity, risk level, significance, and provides recommendations for management or action.
In Perth, arborist reports are a critical part of tree management. They are required by councils for tree removal applications, by developers for planning approvals, by insurance companies for claims, and by property owners who need professional advice about their trees. A well-prepared arborist report can mean the difference between an approved and refused application.
The quality and type of report you need depends on your situation. A straightforward council tree removal application may only need a basic visual assessment, while a legal dispute or high-risk tree near a school may require an advanced Level 5 assessment with quantified risk analysis.
Types of Arborist Reports
Arborist assessments follow a tiered system based on the level of investigation required. Here are the main types used in Perth:
Visual Tree Assessment (VTA)
A basic ground-level visual inspection of the tree. The arborist observes the tree's crown, trunk, and visible root zone for signs of defects, disease, or decline. This is the most common type of assessment for routine council applications where the tree is clearly dead, dying, or has obvious structural issues.
Best suited for: Straightforward council removal applications, basic tree health checks, initial assessments to determine if a more detailed report is needed.
Basic Tree Assessment
A more thorough ground-level assessment using basic tools such as a mallet for sounding (detecting internal decay), a probe for checking soil conditions, and binoculars for crown inspection. The arborist documents species, dimensions, health indicators, structural features, and provides a risk rating using a standardised framework.
Best suited for: Standard council tree removal applications, development applications with a small number of trees, pre-purchase property assessments.
Detailed Tree Assessment
An in-depth assessment that may include limited invasive testing such as increment boring, aerial inspection (climbing or drone), and detailed root zone investigation. Provides a comprehensive analysis of the tree's structural integrity and a detailed risk assessment. Includes mapping of defects and quantified measurements.
Best suited for: Complex development applications with multiple trees, trees near critical infrastructure, insurance claims requiring detailed evidence, disputed council decisions.
Advanced Assessment (TRAQ)
The most comprehensive level of tree assessment. Uses advanced diagnostic tools including resistograph drilling (measuring internal wood density), sonic tomography (creating cross-sectional images of internal structure), root radar, and detailed biomechanical analysis. Produces quantified risk data and is prepared to evidentiary standards.
Best suited for: High-risk trees near schools, hospitals, or high-traffic areas. Legal disputes and expert witness matters. Trees of exceptional significance. Situations requiring quantified risk probabilities.
When Do You Need an Arborist Report?
There are many situations where an arborist report is either required or strongly recommended in Perth:
Council Tree Removal
Most Perth councils require an arborist report when you apply to remove a tree protected under their Tree Preservation Order or local planning policy. Without a report, your application is likely to be refused.
Development Applications
Any development application (DA) affecting an existing tree, or where trees are on or adjacent to the site, typically requires an arborist report assessing all trees and recommending retention, removal, or protection measures.
Insurance Claims
If a tree has caused damage to property or a tree has been damaged by a storm, your insurance company may require an arborist report to assess the cause, extent of damage, and recommended remediation.
Neighbour Disputes
Disputes about overhanging branches, root encroachment, or tree-related damage are best resolved with an independent arborist assessment. The report can be used in mediation or legal proceedings.
Pre-Purchase Assessment
Before buying a property with significant trees, an arborist can identify potential liabilities such as structural risks, root damage to infrastructure, or significant future maintenance costs.
Construction Near Trees
If you are building or renovating near existing trees, an arborist report can specify tree protection zones, root management strategies, and construction methodology to protect retained trees.
What Does an Arborist Report Include?
A standard arborist report in Perth will typically include the following sections:
- Tree identification: Species name (common and botanical), estimated age, and provenance (native, exotic, or endemic).
- Dimensions: Height, canopy spread, trunk diameter at breast height (DBH), and trunk circumference.
- Health assessment: Crown density, leaf colour, dieback extent, pest and disease presence, and overall vigour rating.
- Structural assessment: Trunk condition, major limb integrity, co-dominant stems, included bark, cavities, decay, lean, and root plate stability.
- Risk rating: Using an industry-standard framework (such as QTRA or ISA TRAQ), the arborist assigns a risk rating based on the likelihood of failure, size of failing part, and target exposure.
- Significance assessment:Evaluating the tree's environmental, heritage, amenity, and landscape value using criteria relevant to the council's policy.
- Site context: Proximity to buildings, infrastructure, boundaries, and other trees. Impact of the tree on its surroundings.
- Recommendations: Clear recommendations for retention, removal, pruning, or ongoing management, with justification for each.
- Photographs: Annotated photos showing the tree, any defects or concerns, and the surrounding context.
- Site plan: A plan or aerial image showing the tree location relative to the property and surrounding features.
Choosing a Qualified Consulting Arborist
Not all arborists are qualified to write reports. There is an important distinction between a practical arborist (who performs tree work) and a consulting arborist (who assesses trees and prepares reports). When choosing a consulting arborist for your report, look for:
- Minimum Diploma of Arboriculture (AQF Level 5) for consulting work. A Certificate III (AQF Level 3) qualifies someone for practical tree work but is not sufficient for report writing.
- Arboriculture Australia membership (formerly International Arboriculture Association of Australia). This demonstrates ongoing professional development and adherence to industry standards.
- ISA TRAQ certification for advanced risk assessments. This is the gold standard qualification for tree risk assessment.
- Local council experience. An arborist who has worked with your specific council understands their requirements and can tailor the report accordingly.
- Professional indemnity insurance. A consulting arborist should carry professional indemnity insurance to cover their professional opinions.
Perth Tree Removers connects you with consulting arborists who meet all these criteria. We only refer to professionals with the appropriate qualifications and experience for your specific needs.
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