Tree Protection Plan

Different documents, produced at different stages, and routinely confused because both deal with the same trees. The arboricultural impact assessment comes first and looks outward from the design: what this build does to each tree, which ones can realistically be retained, and what has to change. It is an assessment, and it is what council reads when deciding the application.

The protection plan comes after that question is settled and looks inward at the site: given these trees are being kept, here is exactly how they are protected while the work happens. It is an instruction set, and it is what the site builds to.

Most projects carrying an impact assessment condition need both, and they are commonly conditioned together — the assessment to get the approval, the protection plan to start work under it.

The protection zone is the input the plan is drawn from. Under AS 4970:2025 the calculated area around a tree is the Notional Root Zone — twelve times the trunk diameter measured at 1.4 m, capped at a 15 m radius — and inside it sits the smaller Structural Root Zone holding the roots that keep the tree standing. “Tree protection zone” now refers to the area actually fenced on site, which is what the plan sets out.

Those two figures decide where the fence line goes and whether any part of your build encroaches. Work them out before anything else: the TPZ calculator does the arithmetic for both zones and tells you whether an encroachment is minor, moderate or major.

The fence line is the plan's single most important instruction, because everything else follows from where it sits. Inside it the ground becomes a no-go area: no plant, no stockpiled material, no site shed, no parking, no concrete washout. Outside it the site runs normally, which is the point — a protection zone drawn properly protects the tree without sterilising the lot.

The plan names the fence type, its height and the signage on it rather than leaving it to whatever is on the truck. Rigid mesh panels on feet are the standard answer; bunting and para-webbing are not fencing and do not satisfy the specification. Half a day before plant arrives is the usual cost, and it is the first thing a council officer looks for on an early site visit.

Sometimes the only access route to the back of a site crosses a protection zone. Rather than refuse it, the plan specifies how: a mulch layer spreading the load, and track matting or steel plates over the top, so wheel loads do not compact the soil the roots are breathing in.

What this buys you is the access at all. The cost is the material and a day either end to lay and lift it, which is cheap against rerouting a site. The reason it is not optional is that compaction is invisible and effectively permanent — soil does not loosen again on its own, and the tree shows the damage long after the plates have gone.

The list that settles arguments before they start. Prohibited inside the zone: storing or stockpiling anything, parking, refuelling, mixing or washing out concrete, disposing of any liquid, siting sheds or amenities, excavating, and changing levels in either direction. Concrete washout is the one that catches people — it is strongly alkaline, it goes straight into the root zone, and a tree rarely recovers from it.

Permitted, generally with conditions attached: hand excavation, mulching, and monitored access over installed ground protection. Read at the pre-start meeting this section costs your programme nothing at all. Discovered after the fact it costs whatever the remediation costs.

Where an approved encroachment means digging inside the zone, the plan sets out the method rather than leaving it to the operator. That means exposing roots by hydro-excavation or by hand instead of with a bucket, a limit on which roots may be cut and at what diameter, how those cuts are made and treated, and who directs the work at the open face while it is open.

It is slower per metre than an excavator, over what is usually a short length, and it is priced into the job in advance rather than discovered halfway through. What it prevents cannot be undone: a bucket through a structural root is not a defect you come back and fix.

The schedule of when somebody has to look. Verification that the fencing is up and in the right place before plant arrives, attendance where excavation comes near roots, and inspections at whatever stages your conditions nominate.

Hold points genuinely hold — work at a nominated one cannot proceed until it has been attended and recorded, and two to three business days’ notice is normally enough to schedule an attendance. Hand over the programme early and they go in the diary against your dates instead of against availability. The payoff is at the end: certification becomes a matter of producing a record rather than reconstructing one.

Councils do issue them where protection conditions are being breached, and they stop the site rather than only the work near the tree. Every trade booked that week is affected, and restarting is not a phone call — it takes an agreed remediation position first. The headline cost is the days lost. The real cost is usually resequencing everything that was booked behind them.

Contravening a development approval is an offence in its own right under section 164 of the Planning Act 2016, carrying a maximum penalty of 4,500 penalty units — $777,150 at the current $172.70 a penalty unit. Damaging a protected tree is then a separate offence under the council's own local law whatever approval you hold: in Brisbane the maximum under section 7(3) of the Natural Assets Local Law is $86,350 for an individual and $146,795 for a company.

Those are maximums available to a court rather than fines handed out at the gate, and most breaches are dealt with well below them. The point is the scale the exposure sits on, and that it is two exposures rather than one.

The one that arrives late. A tree with severed roots or a compacted root zone frequently does not die that season — it declines over two or three years, well after practical completion and often after the defects period has closed. Where a condition required that tree to be retained, losing it is a failure to meet the condition even though the build is finished.

What follows is replacement planting to whatever the council conditions, which for a mature tree means advanced stock plus establishment watering rather than a tube stock and a stake. Some councils value the lost tree rather than simply replacing it. Either way the liability follows whoever carried out the works.

The quiet one, and the one that bites hardest on a programme. Where a condition requires arborist certification at a hold point and nobody attended, the stage does not close. The work may be perfectly good — it is the certification that is missing, and it cannot be issued retrospectively by somebody who was not there to see it. The same applies to the final vegetation sign-off, which is commonly on the critical path to your compliance certificate.

A protection plan is the specification. Enforcing it on site and giving that certification is the project arborist role. Where your conditions require both, having the same practice write the plan and supervise the build closes the gap between what was specified and what is being signed off.