Building a new structure, whether it’s a home, a garage, or a commercial development, involves more than just checking the soil.

One critical step that’s often overlooked is the need for a thorough root investigation.

Ignoring what's happening below the surface—especially near large trees—can lead to expensive problems like structural damage, legal disputes, or failed permit applications.

In this article, we’ll explore what root investigation is, why it's so important, and when you absolutely need it.

Quick Overview: Why Root Investigation Matters

• Root investigations help prevent damage to foundations, pipes, and retaining walls.
• They are often required for council approval, especially near protected trees.
• A root investigation identifies the location, depth, and spread of tree roots—so you can build safely around them or take proper mitigation steps.
• Builders, landscapers, and homeowners benefit from early detection of root risks.
• Skipping this step can lead to delays, extra costs, or future legal trouble.

Want to dive deeper? Keep reading to see when, how, and why root investigations make all the difference.

What Is a Root Investigation?

A root investigation is a non-destructive examination of the area around existing trees (usually with a focus on larger or significant trees) to map out the position and depth of their root systems.

The process typically involves:

• Visual inspection by a qualified arborist.
• Use of ground-penetrating radar (GPR) or air spades to safely expose roots.
• Detailed mapping and reporting of where roots exist relative to proposed building works.

The goal? To assess the potential impact of construction on trees—and vice versa.

Why Root Investigations Are Essential Before Building

1.To Avoid Structural Damage

Tree roots naturally seek moisture and can extend far beyond the tree canopy. When roots grow near or under buildings, they can:

• Disrupt or crack foundations
• Uplift driveways or paved areas
• Interfere with plumbing or underground services

Did You Know?

Some tree roots can grow more than 2–3 times the diameter of the tree's canopy—well into build zones that might seem safe.

2.To Comply With Council Regulations

Many local councils across Australia require root investigations as part of a

Development Application (DA) when building near trees—particularly those listed on a Tree Preservation Order (TPO).

Skipping this step can result in:

• DA rejection or costly delays
• Legal fines for root damage
• A requirement to redesign your building plans

Pro Tip:

A certified arborist’s report from a root investigation can often strengthen your application and fast-track approval.

3. To Prevent Cost Blowouts Down the Line

If tree roots are discovered late—after excavation begins—you might be forced to:

• Redesign footings or slab layouts
• Install root barriers
• Halt construction until tree assessments are completed

These unexpected works can add thousands of dollars to your budget.

Bold takeaway: Spending a little on root investigation early can save you a fortune in reactive work later.

Quick Guide: Planning to Build Near Trees? Here’s What to Know

Let’s say you’re planning a home extension near a mature gum tree. You assume the roots won’t reach your new slab… until the builder discovers them mid-dig.

Common Challenges:

• Are the roots going to damage my foundation?
• Will removing them kill the tree and breach council laws?
• Do I need council approval to trim roots or build nearby?

How to Solve It:

1. Get a Root Investigation Early: Schedule a root mapping session with a consulting arborist before finalising your plans.
2. Design Around the Tree: Adjust footing design (e.g. pier-and-beam instead of slab) to avoid major roots where possible.
3. Use Root Barriers: Install physical barriers to redirect future root growth away from structures.
4. Consult Council Guidelines: Work with your arborist to prepare a compliant report that meets your local council’s requirements.

Why It Works:

You reduce the risk of delays, council pushback, or damage to significant trees. It also keeps your build timeline and budget on track.

Need help figuring out where to start? Talk to a certified arborist in your area before finalising your plans.

Who Needs a Root Investigation?

Root investigations aren’t just for large commercial builds. You may need one if you’re:

• Building near a protected or heritage-listed tree
• Planning a driveway, pool, or retaining wall close to existing trees
• Submitting a DA in a council with Tree Protection Zones (TPZs)
• Concerned about damage from existing tree roots

Even minor landscaping work can unintentionally harm root systems if not assessed properly.

What Happens If You Skip It?

Here’s what you might face without a root investigation:

• Unexpected excavation delays
• Tree decline (and replacement fines for protected species)
• Foundation movement or cracking
• Legal disputes with neighbours or council

Reduced property value due to poor tree management or visible damage

Frequently Asked Questions

Do I need council approval for a root investigation?

No, the investigation itself doesn’t usually require approval. However, the results may be submitted as part of your DA, especially if they show how construction will avoid damaging protected trees.

How long does a root investigation take?

Most on-site investigations can be completed in a few hours, but the report and analysis may take a few days depending on complexity and tree size.

Tip: Schedule this step early in your planning phase to avoid project hold-ups.

Can tree roots really cause foundation cracks?

Absolutely. Roots can dehydrate the soil beneath footings, leading to subsidence or heaving. This causes uneven settling, cracking walls, and long-term structural issues—particularly in clay soils.

Is cutting roots a good solution?

Not always. Cutting roots without a proper plan can destabilise the tree or even kill it. That’s why root investigations help you identify safe options, like building around the roots or using engineered solutions.

Conclusion: Don’t Dig Blind

Whether you’re extending a home, adding a driveway, or developing a multi-unit site, a root investigation should be part of your standard pre-build checklist. It’s about protecting your build, your budget, and the environment around you.

By understanding what lies beneath the surface, you avoid surprises that could delay your project or create legal headaches.

Bottom line? If you’re building near trees—especially mature or protected ones—don’t risk skipping a root investigation