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Tree Protection Zone advice
Sometimes you do not need a report. You need to know whether the extension you are drawing lands inside the root zone, and if it does, by how much. This is that answer, in writing, quickly.
Fixed quote within one business day · agreed in writing before any work starts
What you get
- DSH measured properly, at 1.4 m, and multi stem combined where relevant
- NRZ calculated to AS 4970:2025, with the clamps applied
- SRZ calculated, because any intrusion into it is a major impact regardless of the NRZ figure
- Encroachment expressed as a proportion of NRZ area, and which band that puts you in
- A plain answer on whether the proposal as drawn is likely to be acceptable
- What the next step is, if there needs to be one
The 2025 change most people have not absorbed
Under the previous standard the calculated zone was the TPZ. Under AS 4970:2025 the calculated zone is the Notional Root Zone, and the TPZ is the area actually protected on site, which the project arborist determines. Encroachment is assessed against NRZ area, banded as minor at 10% or less, moderate above 10% and up to 20%, and major above 20% or on any SRZ intrusion.
Six of the eight best known consultancies in Melbourne still do not mention the 2025 revision anywhere on their websites, and Council Arboriculture Victoria's public calculator is still built on the 2009 formulas. If your figures came from either, they are worth checking.
When this is not enough
This is advice on a zone, not a lodgement document. If you are applying for a planning permit you will need an impact assessment, and the fee for this is credited toward it if you go ahead within three months.
There is also a free NRZ and SRZ calculator on the TIMBR Field site if you would rather run the numbers yourself. It is built to the 2025 formulas and it costs nothing.
Common questions
What is the difference between NRZ and TPZ now?
NRZ is the calculated zone, from DSH multiplied by twelve, clamped between two and fifteen metres. TPZ is what you actually fence on site, set by the project arborist from the NRZ plus site conditions. Under the 2009 standard those were the same thing, which is why the change catches people.
Can you do this without visiting the site?
Only if you can give me an accurate DSH measured at 1.4 m and a dimensioned plan. Most of the errors I see come from a trunk measured at the wrong height, so I would usually rather measure it.
Is the fee credited if I need a full report?
Yes, toward an impact assessment on the same site within three months. Say so when you enquire and it will be written into the quote.
Other services
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ResidentialArboricultural Impact Assessment
DevelopmentClause 52.37 Canopy Tree Report
Residential · PlanningPreliminary Tree Assessment
Before you designTree Protection Management Plan
DevelopmentRoot & Infrastructure Investigation
InvestigationArboricultural Supervision
On siteConstruction Monitoring
On siteTree Risk Assessment
TRAQ qualifiedSend me the plans and I will send you a number.
Fixed fee, quoted in writing within one business day, scope written down. If it turns out you do not need this report, I will tell you that instead.