A tree barrier is a sheet of plastic buried alongside a tree that physically redirects roots away from your driveway, pipes and foundations.

Tree roots crack concrete, lift paving and punch through sewer lines. The repairs are expensive, and they keep recurring unless you stop the roots reaching the structure in the first place.

This guide explains how tree barriers work, which Australian trees cause the worst damage, and how to pick the right tree barrier depth for your project.

What Is a Tree Barrier?

A tree barrier (also called a root barrier) is a vertical sheet of high-density polyethylene (HDPE) installed in the ground between a tree and whatever you want to protect. When roots hit the barrier surface, they can't push through. Instead, they follow the sheet downward and continue growing beneath the protected structure.

The tree stays healthy, the roots keep growing, and your driveway stays flat. It's a simple concept that solves what would otherwise be a recurring, expensive problem.

Most tree barriers sold in Australia are UV-stabilised HDPE, around 1mm thick, and come in 50-metre rolls. All Stake Supply stocks three depths: 450mm, 500mm, and 600mm.

The big advantage over other root management methods is permanence. Root pruning means re-cutting every few years as roots regrow. Chemical treatments break down over time.

A properly installed HDPE barrier lasts decades with zero maintenance. That alone makes it the preferred option for councils, civil contractors and property owners across Australia.

• Redirects root growth downward, not sideways into structures
• Made from UV-stabilised HDPE rated for Australian conditions
• No chemicals, no ongoing treatment, no repeat costs
• Available in 450mm, 500mm, and 600mm depths
• Sold in 50-metre rolls for continuous, unbroken runs

Which Trees Cause the Most Root Damage in Australia?

Not every tree needs a barrier. Some species barely spread their roots beyond the canopy drip line. But others are notorious for sending roots 20 or 30 metres sideways through soil, cracking everything in their path.

If you have any of the species below within 10 metres of built infrastructure, a tree barrier is worth installing before the damage bill arrives. The Australian Department of Climate Change, Energy, the Environment and Water recommends root management planning for any tree planted within 3 to 5 metres of built structures.

Willows are the worst offenders for pipe damage because they actively seek out moisture. A single willow root can travel 40 metres underground to reach a leaking sewer joint. Figs are the worst for structural damage, with root systems powerful enough to lift and crack reinforced concrete.

For more on managing aggressive species, read our guide on managing invasive tree roots.

How Does a Tree Barrier Redirect Roots?

Roots grow towards water and nutrients along the path of least resistance. When a spreading root meets a solid HDPE barrier, it can't penetrate the sheet. The root follows the barrier face downward until it passes below the bottom edge.

At that depth, the root continues sideways, but it's now deep enough to pass safely under driveways, footpaths and pipe runs. According to research published by Plateau Trees, most infrastructure damage occurs in the top 300 to 500mm of soil, which is exactly where barriers do their work.

This is why barrier depth is the single most important decision. A 450mm barrier stops root damage in the top 450mm of soil, which is where most infrastructure sits. For larger trees with aggressive root systems, a 600mm barrier gives you a bigger safety margin.

Read our detailed breakdown of how root barriers work for the full picture.

A properly installed tree barrier protects:

• Concrete driveways and footpaths
• Building foundations and slab edges
• Sewer pipes and stormwater drains
• Retaining walls and garden edging
• Swimming pools and pool surrounds
• Paved entertaining areas and pathways

Choosing the Right Tree Barrier Depth

The right depth depends on two things: the size and species of tree, and how critical the infrastructure is. A small ornamental near a garden bed is a different situation from a mature eucalypt 5 metres from your sewer main. All Stake Supply stocks three standard depths to cover the range.

• 450mm depth suits smaller ornamental trees, garden borders, and low-risk areas where roots travel close to the surface. The Root Barrier 450mm x 50m Roll handles most residential garden jobs.
• 500mm depth is the popular middle option for medium natives and trees planted near footpaths or light paving. The Root Barrier 500mm x 50m Roll is what most suburban landscapers reach for.
• 600mm depth is what you need for large eucalypts, figs, willows, and any tree near sewer lines or building foundations. The Root Barrier 600mm x 50m Roll is the standard council and civil contractor specification.

When in doubt, go deeper. The material cost difference between a 450mm and 600mm roll is minor compared to the cost of repairing a cracked slab or replacing a collapsed drain. For projects where you need to join multiple rolls end-to-end, seal the seams with butyl bond tape to create a continuous, root-proof run.

Where to Install a Tree Barrier on Your Property

The barrier runs between the tree and the structure you're protecting. Not in a ring around the tree (that restricts the root zone too much and can destabilise it), but as a straight or gently curved line along one side. Think of it as a fence underground.

Follow these placement guidelines for a barrier that actually works:

1. Keep the barrier at least 1.5 metres from the trunk to avoid choking the root zone
2. Extend the barrier 2 metres past the structure on each side (roots will route around short barriers)
3. Set the top edge just below ground level so it's not visible on the surface
4. Run the barrier along the full length of whatever you're protecting, not just the section nearest the tree
5. Overlap and seal any joins with butyl tape so roots can't push through gaps

For new plantings, install the barrier before the tree goes in the ground. It's straightforward when the trench is already open. For established trees, you'll need to trench alongside the existing root zone, and you may need to cut some existing roots.

Our root barrier installation guide walks through both scenarios step by step. If you're working around a significant tree, it's worth getting an arborist assessment first to map the root zone before digging.

Tree Barrier vs Removing the Tree

When roots start cracking concrete, the first instinct is often to remove the tree entirely. That solves the root problem, but it creates others: loss of shade, reduced property value, potential council fines for removing significant trees without approval, and a big hole in your yard. A tree barrier is almost always the smarter first option.

Costs listed are approximate guides only and vary by project scope, tree size, and location. Contact All Stake Supply for an accurate quote on barrier materials.

Tree removal only makes more sense when the tree is already structurally compromised, is growing directly against a foundation wall with no room for a barrier, or is a declared weed species your council wants gone. For everything else, a barrier is more cost-effective, faster to install, and keeps the tree intact.

Order Tree Barrier Products in Australia

All Stake Supply has stocked root barrier and erosion control products from their St Marys warehouse in western Sydney since 1976. With over 1,000 products in stock, they carry every barrier depth plus the accessories you need to finish the job properly.

All three barrier depths ship Australia-wide with a guaranteed complete delivery, so your project materials arrive together rather than in partial shipments that stall jobs on site. That matters when you've got a trench open and a tree to protect against.

Browse the full product range or contact the team for trade pricing and bulk orders.