Australia has its own dedicated standard for this, and it maps closely enough onto BS 5837 that a UK-trained arborist will recognise the shape of it immediately: AS 4970-2009, Protection of trees on development sites. If a development application in Australia sits near a tree worth retaining, a council will typically expect an assessment against it before the application progresses.
Two zones, not one
Where BS 5837 works from a single Root Protection Area, AS 4970 works from two related but distinct calculations:
- Tree Protection Zone (TPZ) — the primary exclusion area. Radius = trunk diameter (measured at 1.4 m, the Australian standard's specified height) × 12. As with BS 5837's RPA, this is a calculation from a measured diameter, not an estimate — the standard sets a minimum radius of 2 m and generally caps it in line with the tree's dimensions.
- Structural Root Zone (SRZ) — a tighter, non-negotiable zone closer to the trunk, calculated from trunk diameter above the root buttress using its own formula. Where the TPZ can sometimes be encroached on with a method statement, the SRZ is the line that protects the tree's structural stability and is treated far more strictly.
A survey that only reports a TPZ and skips the SRZ calculation is incomplete against the standard — council arborists reviewing development applications will ask for it specifically.
Encroachment needs a method, not a request
AS 4970 allows minor TPZ encroachment where a qualified arborist can demonstrate the tree will remain viable — but that demonstration has to be a documented method statement (root mapping, hand excavation near roots, protective fencing detail), not a line in an email asking the council to make an exception. The standard is explicit that unassessed encroachment is not compliant, regardless of how minor it looks on a plan.
What a council arborist is actually checking
The same three things a UK planning officer checks under BS 5837: does the schedule match the plan, does every TPZ/SRZ trace back to a diameter actually measured on site at the standard's specified height, and is any encroachment backed by a method statement rather than assumed. Get those three right and an Australian development application clears tree referral about as fast as anywhere else.
This isn't legal advice — always confirm current requirements with the relevant council. tree·canopy is built to keep the schedule and the plan generated from the same field record, so the TPZ and SRZ on the drawing always trace back to a diameter someone actually measured.