Case Study: Regulated & Significant Trees

As Adelaide continues to grow and change, one of the recurring challenges in urban planning is how we treat trees in our residential suburbs. Trees add character, shade and habitat, but they can also create genuine constraints – from damage to buildings through to limits on how land can be subdivided and developed.

In the past few months, Urban Horizons has worked on two very different tree-related matters that show how planning, arboriculture and property intersect. Both cases highlight that the best outcomes usually come from a careful, step‑by‑step process, with the trees considered from the outset.

Case Study 1: Removal

In the first matter, our client asked for help preparing an assessment report for a tree they believed was causing damage to their property. The key question: does this tree meet the tests for removal under the relevant planning policy, and can that be clearly justified?

To answer that, Urban Horizons followed the standard, two-step process as outlined by the Environment, Development and Resources Court in the past:

• Step 1: Is the tree worthy of being retained?

  Before even considering whether the tree is healthy, or causing damage to a building, the first part of the test seeks to answer a simple question: Is the tree worth retention? Does the tree provide environmental or aesthetic benefit such that it’s retention is warranted?

  To answer this question, we undertook a simple site visit, identified the species of tree, took photos of the subject land, and considered if retention was warranted. Ultimately, we determined that there were various more notable trees in the immediate locality, and the tree itself did not provide sufficient environmental or aesthetic benefit to warrant it’s retention.

  Whilst the first part of the test was satisfied, our client had already sought a structural engineers report which found that the tree was causing damage to their property. Given the report had already been created, we still opted to answer the second question:

• Step 2: Are there circumstances that warrant the removal of the tree?

  In this case, the circumstances were evident: The tree was causing substantial damage to the client’s property. Ordinarily, Relevant Authorities will seek evidence that this is the case through a structural engineers report. In this case, we referred to, and highlighted the evidence within the structural engineers report to clearly highlight that in this situation, the tree is required to be removed to prevent further damage.

Ultimately, with the above points combined, we were able to provide a convincing argument to the Relevant Authority, that the removal of the tree was warranted. The above approach illustrates that in the case of removal, an Arborist report may not always be necessary.

Case Study 2: Preliminary Advice & Land Division

The second matter involved a different type of challenge: a large, Council owned street tree was near to the site boundary which had the potential to affect the feasibility of the site.

Here, the focus was on early advice rather than a full removal assessment.

• Recognising the constraints: NRZ and SRZ
  Trees have a ‘Notional Root Zone’ and a ‘Structural Root Zone’, which both affect the potential building envelope. In simple terms:

  • The NRZ represents the area where most of the tree’s fine absorbing roots are likely to be, and where excavation or building can stress the tree. The NRZ can be a radius up to 15m from the trunk of the tree in some cases. Encroachment into the NRZ will generally require advice from an Arborist to determine the permissible percentage based on the species and health of the tree.

  • The SRZ is closer to the trunk and covers the structural roots that keep the tree upright and stable.

Any future building footprints, driveways, service trenches or private open space needed to respect these zones. If future lots or dwellings can’t be designed without significantly encroaching on the NRZ or SRZ, then subdivision becomes more difficult to justify.

• Next step: early arborist advice
  At the preliminary stage, the most helpful action for the client was not to draw dozens of concept plans but to commission early arborist advice. An experienced arborist can:

  • Accurately map the NRZ and SRZ based on the tree’s species, trunk diameter and site conditions.

  • Advise on acceptable levels of encroachment, if any, and suitable construction techniques (e.g. pier and beam, permeable paving) to minimise impact.

  This arborist input then feeds directly into planning and design. Instead of guessing where the tree’s roots might be, subdivision concepts can be drafted with a clear understanding of what is possible and what is likely to attract council support.

• Exploring “work around” options and land division likelihood
  With tree constraints clearly understood, the next step is to test how much layout flexibility exists on the site. Some options we explored included:

  • Relocating proposed dwellings or garages further from the tree.

  • Altering the location of driveways to avoid the NRZ.

  • Designing and orienting private open space to integrate the tree as a feature over a courtyard, rather than treating it as an obstacle.

  In this matter, the advice covered not just what could be designed, but also an honest appraisal of land division likelihood. Councils are generally more supportive of subdivision proposals where regulated and significant trees are retained and meaningfully integrated into the layout. By front‑loading the advice, the client was in a position to make an informed decision before spending heavily on detailed design.

Key Lessons:

These two matters are different, but they share a common theme: trees often sit at the intersection of private expectations and public policy. For owners and developers, a tree might be a source of worry; for councils, it’s part of broader urban character and environmental goals.

Getting clear advice early helps to:

• Reduce uncertainty about what is realistically possible on a site.

• Avoid unnecessary design fees on concepts that are unlikely to be supported.

• Provide council with transparent, technically grounded information, whether the goal is removal, retention or subdivision.

For clients in Adelaide dealing with trees and planning issues – from suspected building damage to future land division around significant trees – a structured, step‑by‑step approach can make the process far more predictable.

If you’re looking at a site with tree constraints and aren’t sure what’s possible, feel free to get in touch to discuss a preliminary review, arborist coordination and planning advice tailored to your project.