How An Arborist Assesses Tree Risk & Structural Stability

Trees are valuable assets, but they can also create real risk when defects go unnoticed. A falling limb can injure someone, damage roofs and cars, or block access after a storm. For property owners, there is also the question of responsibility. If a tree is clearly failing and nothing is done, that can create avoidable consequences.

A risk assessment helps you make practical decisions based on evidence rather than assumptions. It also supports better planning, whether you need targeted pruning, staged removals, emergency response, or an arborist report for approvals.

A tree risk assessment is commonly used to:



• Identify hazards before they fail
• Reduce risk around homes, sheds and driveways
• Support safer public access on commercial sites
• Provide documentation when needed for property decisions

Before an arborist even looks closely at the tree, they consider what is around it. A defect matters far more if it is over a footpath, a play area, a car space, or a busy access route. The same crack in a limb might be low risk in a back paddock and high risk over a roofline.

This early step helps define priorities and the level of detail required. It also influences the recommendation, because the safest option is not always full removal, sometimes it is reducing the canopy load over a target area.

Site assessment usually involves:



• Identifying people and property that could be impacted
• Noting access constraints for safe work
• Reviewing slope, drainage and soil conditions
• Considering exposure to wind and storms

A professional arborist starts with a systematic visual inspection. They assess the tree as a whole first, then work through the trunk, the crown and the root zone. This is not a quick glance, it is a methodical check for patterns and warning signs.

They look at the tree’s overall form, whether it is balanced, whether it has developed heavy side loading, and whether the canopy is supporting deadwood that could drop without warning. They also look for changes that suggest stress, such as thinning foliage, epicormic growth, or poor leaf colour.

Common canopy and trunk indicators include:



• Deadwood in the crown
• Cracks, splits, or weak junctions
• Cavities, hollows and decay features
• Fungal fruiting bodies on trunk or base

Structural stability is often determined at junction points. This includes where major limbs attach, where the trunk divides, and where multiple stems are competing. Weak unions can form when bark becomes trapped between stems, or when a branch union is poorly supported by wood.

Arborists assess angles, attachment strength and how weight is distributed. They also look at previous pruning, because poor cuts can cause decay pathways and regrowth that is heavy but weakly attached.

Structural checks often focus on:



• Co dominant stems and included bark
• Over extended limbs with end weight
• Previous lopping wounds and decay pockets
• Rapid regrowth that increases leverage

A tree’s stability depends heavily on the base and roots. If the root plate is compromised, failure can happen suddenly, particularly after heavy rain when soils soften. Arborists examine the ground around the tree for heaving, cracking soils, exposed roots, or signs of recent movement.

They also assess the trunk flare, because a healthy flare indicates stronger support. If the flare is buried, damaged, or shows decay, stability can be reduced. In Ballina’s variable soils, waterlogging and erosion can also weaken root structure over time.

Root zone assessment can include:



• Soil heave or gaps near the base
• Root damage from excavation or vehicles
• Drainage issues and waterlogged soils
• Signs of termites or borer activity

Hazardous trees rarely fail without warning signs. The key is knowing which signs are cosmetic and which indicate structural weakness. Arborists are trained to interpret defects in context. A small cavity might be stable if the tree has strong remaining wood, while a similar cavity in a stressed tree with a heavy canopy could indicate higher risk.

They also consider how defects interact. For example, decay plus heavy end weight plus high wind exposure is a different scenario than decay alone.

Defects commonly linked to failure risk include:



• Advanced decay at branch unions
• Long cracks along the grain
• Significant leaning with disturbed root plate
• Major canopy dieback or dead tops

Tree risk is not only about defects, it is also about species behaviour. Some species shed limbs more readily, some develop brittle wood as they age, and some respond poorly to heavy pruning. A qualified arborist uses local knowledge to interpret what is normal for that species and what is a red flag.

In a coastal environment, salt exposure, wind loading and fast growth can shape tree structure differently compared to inland conditions. Understanding how a species typically grows helps the arborist predict how it will respond to reduction pruning or ongoing maintenance.

Species and growth considerations include:



• Typical strength of timber and branch unions
• Growth rate and canopy density
• Likelihood of limb drop in heat or after rain
• Response to pruning and wound closure

Most assessments begin visually, but arborists can also use tools to gather more information where appropriate. This might include sounding the trunk to detect hollows, probing cavities carefully, or using measuring tools to quantify lean and canopy spread. In some cases, elevated work platforms are used to inspect higher sections safely.

The goal is not to make the assessment complicated, it is to make it accurate. Tools are used when the visual picture is incomplete, or when the consequences of failure are high.

Extra assessment methods may include:



• Measuring lean and canopy load
• Close inspection of unions at height
• Detailed documentation for arborist reports
• Photographic records for monitoring changes

Risk is not just whether a tree might fail, it is also what happens if it does. Arborists weigh the likelihood of failure, the part of the tree that could fail, and the consequences based on what is nearby. A large limb over a driveway with frequent use carries higher consequence than the same limb over an unused corner of the yard.

This is why professional risk management is so valuable. It is not fear-based, it is a balanced decision-making process that aims to reduce risk sensibly.

Risk considerations usually include:



• Likelihood of failure within a given time frame
• Size of the failing part and expected impact
• Frequency of people or vehicles in the target zone
• Current tree health and rate of decline

A professional arborist will not default to removal unless it is necessary. Often, the best approach is targeted pruning to reduce leverage and weight, removal of deadwood, or clearance pruning to protect roofs and accessways. In other cases, removal is the safest option, particularly if decay is advanced or the root plate is unstable.

For larger properties, land clearing and firebreaks can also form part of broader risk reduction, especially where vegetation density creates hazard during storms or bushfire conditions. Where appropriate, chipping and mulching can turn debris into a useful resource for the property, improving soil moisture retention and reducing waste.

Common risk management recommendations include:

• Structural pruning to reduce canopy load
• Deadwood removal to reduce drop risk
• Full removal for unstable or failing trees
• Ongoing monitoring with scheduled inspections

For many property owners, the most useful outcome is clarity. A good assessment explains what was found, why it matters and what should happen next. Clear documentation is also helpful when dealing with insurers, property managers, or approvals where arborist reports are required.

This is where professional judgement is essential. It is not enough to identify an issue, the advice must be practical, safe and suited to the property.

Documentation can include:



• Photos and notes of key defects
• Clear recommendations and priorities
• Maintenance intervals and monitoring advice
• Formal arborist reports when required

It is tempting to look up at a tree and judge it by appearance, but many structural issues are not obvious to untrained eyes. A tree can look green and full while hiding serious decay at the base, weak unions, or stress from root disturbance.

DIY inspection also carries safety risk. Climbing ladders, cutting limbs, or working near powerlines without training can cause injury. Professional arborists have the equipment, techniques and safety systems to manage hazards correctly.

A professional assessment helps avoid:



• Misjudging defects and leaving hazards in place
• Over-pruning that weakens the tree further
• Unnecessary removal of healthy trees
• Risky work without safe access equipment

At Tallow Tree Services, we help property owners make confident decisions with professional arborist Ballina assessments focused on safety, liability and long-term risk management. Whether you need pruning, removals, emergency response, chipping and mulching, land clearing and firebreaks, or arborist reports, our qualified team delivers careful work with minimal disruption. To organise an assessment or discuss your concerns, visit our website and contact our team today.