What Happens During a Professional Tree Risk Assessment?

If you own a property in Wollongong, chances are there is at least one large tree on or near your land. Between the Illawarra escarpment, the coastal suburbs and the leafy streets of areas like Keiraville, Mount Pleasant and Thirroul, mature trees are part of what makes the region special. They also come with responsibility. Storms, saturated soils, coastal winds and ageing wood can all turn a healthy-looking tree into a hazard. A professional tree risk assessment is the most reliable way to find out whether a tree is safe, and what to do if it is not.

This guide explains what a qualified arborist actually does during an assessment, what they are looking for, and what you can expect afterwards.

What Is a Tree Risk Assessment?

A tree risk assessment is a systematic evaluation of a tree's condition, its surroundings and the likelihood that it, or part of it, will fail and cause harm or damage. It is not simply a case of deciding whether a tree looks healthy. Arborists consider three main questions:

  • How likely is the tree or a branch to fail? This depends on structure, health, species and site conditions.
  • What could be hit if it does fail? Houses, cars, power lines, footpaths, play areas and neighbouring properties all matter.
  • How serious would the consequences be? A falling branch over an unused corner of a paddock is very different from one above a children's play area or a bedroom.

By combining these factors, an arborist can assign a risk rating and recommend proportionate action. Not every tree with a defect needs to be removed, and a good assessment often finds ways to keep a tree safely rather than cutting it down.

Who Should Carry Out the Assessment?

In Australia, tree risk assessment should be performed by a qualified arborist. Look for a Certificate IV or Diploma in Arboriculture (AQF Level 4 or 5), and ideally formal training in tree risk assessment, such as the Tree Risk Assessment Qualification (TRAQ) or a methodology like QTRA (Quantified Tree Risk Assessment) or TRAQ-aligned approaches. Many reputable arborists also hold membership with Arboriculture Australia or Tree Industry Australia.

Always ask for evidence of qualifications and current public liability insurance. If you need a report for council, insurance or legal purposes, confirm the arborist is experienced in writing formal reports.

Step-by-Step: What Happens During the Assessment

1. Initial Consultation and Site History

The process usually begins with a conversation. The arborist will ask why you are concerned and gather background such as:

  • Any recent storm damage, dropped branches or leaning
  • Previous pruning, lopping or topping
  • Nearby construction, trenching, driveway work or changes to ground levels
  • Changes in the tree's leaf density, colour or growth
  • Whether the tree is protected by council or located near a boundary

This history provides valuable clues. Root damage from excavation, for example, can take years to show up in the canopy but may significantly reduce stability.

2. Identifying the Tree and the Site

Next, the arborist identifies the species and notes its size, age class and general form. Species knowledge matters because different trees have different failure tendencies. In the Wollongong area, commonly encountered trees include:

  • Eucalypts such as spotted gum and blackbutt, which can drop limbs without obvious warning
  • Moreton Bay figs and other figs, known for large spreading canopies and aggressive roots
  • Camphor laurels, often with included bark unions and decay in large old specimens
  • Norfolk Island pines, common along the coast and exposed to strong winds
  • Jacarandas, liquidambars and other ornamentals in suburban streets and gardens

The arborist also records site conditions, including soil type, slope, drainage, exposure to wind and whether the tree is part of a group that shelters one another. Removing one tree can suddenly expose its neighbours to wind loads they have never experienced.

3. Identifying Targets and Occupancy

The arborist maps out what lies within striking distance of the tree. These are called targets, and they include buildings, vehicles, fences, powerlines, pathways, outdoor living areas and people. They also consider how often the area is occupied. A tree over a carport used daily has a higher exposure than a tree at the back of a rarely used block.

4. Visual Tree Assessment (VTA)

The core of most assessments is a ground-based Visual Tree Assessment. The arborist walks around the tree, often multiple times, examining it from root crown to canopy tip. They look for:

  • Root zone issues: exposed, cut, damaged or lifted roots, soil heave, fungal fruiting bodies, and signs of compaction or waterlogging
  • Trunk defects: cracks, cavities, bulges, seams, bleeding sap, termite activity, old wounds and signs of decay
  • Branch unions: included bark (where the bark is trapped between two stems, creating a weak joint), co-dominant stems and poorly attached limbs
  • Canopy condition: deadwood, dieback, thin foliage, epicormic shoots, unusual leaf colour and imbalanced growth
  • Lean and movement: whether a lean is long-standing (the tree has adapted) or recent (often a warning sign)
  • Previous pruning: topping, flush cuts and poor pruning wounds that lead to decay and weak regrowth

Many arborists use binoculars to inspect the upper canopy, and photographs are taken to document key defects.

5. Detailed Inspection and Testing

If the visual assessment reveals something concerning, the arborist may recommend a more advanced assessment. Common tools and techniques include:

  • Sounding with a mallet: tapping the trunk to detect hollow or decayed areas by changes in sound
  • Probing: using a thin probe to measure the depth and extent of cavities or rot
  • Resistance drilling: a fine drill bit measures wood density as it passes through the trunk, revealing internal decay
  • Sonic or acoustic tomography: sound waves create an internal image of the trunk to map decay without drilling
  • Root investigation: careful excavation with an air spade to expose roots without damaging them
  • Aerial inspection: a climbing arborist or elevated work platform may be used for a close look at the upper canopy

These methods are not needed for every tree, but they can be crucial for large, valuable or heritage specimens where removal would be a significant loss. They help avoid unnecessary removal by showing exactly how much sound wood remains.

6. Evaluating Likelihood and Consequences

Once the data is collected, the arborist evaluates the likelihood of failure, such as improbable, possible, probable or imminent, and combines it with the likelihood of impact on targets and the severity of consequences. The result is an overall risk rating, often described as low, moderate, high or extreme.

This structured approach keeps the decision objective. It also provides a consistent framework that can be explained to insurers, councils, neighbours or strata committees.

What You Receive After the Assessment

The outcome depends on your needs. For a simple domestic inspection, you may receive a verbal summary and quote for recommended work. For more formal purposes, you will usually receive a written report that includes:

  • Tree species, location, dimensions and condition
  • Defects identified, with photographs
  • Targets and site factors considered
  • The method of assessment used and any limitations
  • Risk rating before and after mitigation
  • Clear recommendations and a suggested timeframe
  • Re-inspection intervals, if the tree is retained

Typical Recommendations

Recommendations are designed to reduce risk to an acceptable level. They may include:

  1. No action required with a re-inspection in one to three years
  2. Selective pruning to remove deadwood, reduce end weight or relieve stress on weak unions
  3. Cabling or bracing to support structurally compromised stems
  4. Soil and root care such as mulching, aeration or restricting access to the root zone
  5. Relocating the target by moving a seating area or parking space out of the fall zone
  6. Partial or full removal where risk cannot be reduced to an acceptable level by other means

Wollongong Council Rules and Approvals

Before any pruning or removal, check whether approval is required. Wollongong City Council regulates tree work under its Development Control Plan and the state planning framework, and many trees, particularly larger ones, those in heritage or environmentally sensitive areas, and those in certain zones, require a permit before work can begin. Properties near the escarpment, riparian corridors or within conservation areas often have additional restrictions.

Under the NSW Tree (Disputes Between Neighbours) Act 2006, neighbours may also seek orders through the Land and Environment Court where a tree is likely to cause damage or injury. A written risk assessment from a qualified arborist is useful evidence in such matters.

Where a tree poses an imminent danger, there are provisions for urgent action, but it is wise to document the hazard with photographs and a written assessment, and to contact council promptly. Trees near powerlines should only be approached by arborists authorised to work near electrical assets. Endeavour Energy manages vegetation near network infrastructure in the Illawarra region.

Your arborist can advise on the current requirements and, in many cases, assist with the application and supporting documentation.

When Should You Book a Tree Risk Assessment?

Consider an assessment if you notice any of the following:

  • Large dead branches or sudden canopy thinning
  • Fungal growth around the base or on the trunk
  • Cracks, splits or hollows in the trunk or major limbs
  • Soil lifting or cracking on one side of the tree
  • A noticeable change in lean after wet weather or storms
  • Recent construction or excavation near the root zone
  • Large trees over buildings, play areas or driveways that have never been inspected
  • Buying or selling a property with significant trees

After severe weather events, including the east coast lows and intense rainfall that regularly affect the Illawarra, a post-storm check can identify damage that is not obvious from the ground. Saturated soil reduces root anchorage, so trees that stood through the storm may still be at greater risk for weeks afterwards.

How Long Does It Take and What Does It Cost?

A basic assessment of a single tree usually takes 30 to 60 minutes on site, with additional time for complex trees, multiple specimens or advanced testing. Written reports are typically completed within a few days to a week, depending on the arborist's workload and the level of detail required.

Costs vary depending on the number of trees, the complexity of the site, whether testing equipment is used and the type of report. Basic inspections are generally modest, while detailed reports with tomography or root investigation cost more. Always request a clear quote in advance and ask what is included.

How to Prepare for the Visit

  • Clear access to the base of the tree, including long grass, rubbish and stored items
  • Note any observations and dates, such as when a branch dropped or a lean appeared
  • Gather records of previous pruning, construction or earlier reports
  • Let neighbours know if inspection will require access to their side of the boundary
  • Secure pets and be present, if possible, to discuss concerns directly

Frequently Asked Questions

Can a tree look healthy and still be dangerous?

Yes. Internal decay, root problems and weak branch unions are often invisible to the untrained eye. A full green canopy does not guarantee structural soundness.

Does a risk assessment always lead to tree removal?

No. Many assessments conclude that a tree is safe https://knoxcvju510.opalvector.com/posts/what-is-an-arborist-a-wollongong-homeowner-x27-s-guide or can be managed with pruning, support systems or changes to the surrounding area. Removal is generally a last resort.

How often should large trees be assessed?

For mature trees near people or property, an inspection every one to three years is a sensible baseline. Trees with known defects, or those in high-use areas, may need more frequent monitoring.

Is a risk assessment a guarantee?

No. Trees are living organisms, and no assessment can eliminate risk entirely. A report reflects the tree's condition at the time of inspection, which is why re-inspection and monitoring are important, particularly after major weather events.

Final Thoughts

A professional tree risk assessment gives you clarity. Instead of guessing whether a tree is a hazard, you get a structured, evidence-based evaluation and a practical plan. For Wollongong property owners, where coastal weather, steep terrain and mature canopy are everyday realities, regular inspections protect people, buildings and the trees themselves. If you have a tree that concerns you, engage a qualified local arborist, ask about their assessment method and make sure any recommended work complies with council requirements. Acting early is almost always safer, simpler and more affordable than dealing with the consequences of a failure.

Wollongong Tree Removal Pros

106 Gipps St, Wollongong NSW 2500

(02) 4210 5945