Report guide
Preliminary Arborist Report (PAR)
A Preliminary Arborist Report is the first-pass tree assessment used early in a project — typically before a development application is prepared — to understand what trees are present, their condition, and how they might constrain a design.
What a PAR typically includes
- A site walk identifying every tree relevant to the proposed works.
- Species, dimensions (DSH, height, canopy spread) and a general health and structure rating for each tree.
- An initial Notional Root Zone (NRZ) and Structural Root Zone (SRZ) for each retained tree, calculated to AS 4970:2025.
- Early retention, removal or further-assessment recommendations to guide site layout.
When you need one
A PAR is usually commissioned at concept or feasibility stage — before detailed architectural or engineering drawings exist — so tree constraints can shape the design rather than be discovered after it's finalised. Many councils expect a PAR (or equivalent) to accompany early pre-application enquiries.
How it differs from an AIA
A PAR assesses the trees on their own; an Arboricultural Impact Assessment goes further, testing a specific design against each tree's TPZ and SRZ to quantify encroachment and recommend mitigation. Most projects progress from a PAR to an AIA once a design is available.
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