The arborist's rule of thumb says tree roots spread outward to 1.5 times the tree's height. Tree roots spread in search of water and nutrients to maintain growth, but this natural process can turn problematic when they grow beneath structures.

When roots become invasive, they can damage foundations, driveways, footpaths and retaining walls. We'll show you how to remove and redirect invasive roots without sacrificing an established tree.

What Are Invasive Tree Roots?

Roots provide trees with stability and nutrients from the soil. The taller the tree grows, the wider and more aggressive the root system becomes.

Invasive roots occur when the root system has grown underneath structures like your house, footpaths, driveways or retaining walls. These roots are remarkably strong and can push or lift anything in their path, including concrete slabs and building foundations.

Damage from invasive roots can cost thousands to repair. Prevention methods when planting new trees are always the best approach, but several effective options exist for managing established trees.

Signs Your Tree Has Invasive Roots

Identifying invasive roots early can save you significant repair costs down the track. Watch for these warning signs around your property.

• Cracks appearing in your foundation, concrete slab or brick walls
• Uneven or lifting pavers, driveways or footpaths
• Visible roots growing above ground near structures
• Doors or windows that suddenly stick or won't close properly
• Blocked or damaged drainage pipes and sewer lines
• Soil movement or settling near the base of walls

If you notice any of these signs, it's essential to act quickly before the damage worsens. Tree roots grow continuously, and small cracks can rapidly expand into major structural issues.

Managing Invasive Roots on Established Trees

If you suspect a tree close to your home or other structure has invasive roots, act quickly before any serious damage occurs. Waiting will only make the problem more difficult and expensive to fix.

For large trees with well-established root systems, get advice from a qualified arborist before starting any work. Incorrectly cutting major roots can destabilise the tree and create safety hazards.

The most effective long-term solution for controlling invasive roots is installing a root barrier. A root barrier is a physical shield installed 600mm to 1000mm into the ground that prevents tree roots from growing outwards in unwanted directions.

The barrier forces roots to grow downward and away from areas they could damage. This protects your infrastructure while keeping the tree healthy and stable.

Depending on the location of your tree, the root barrier can be installed in a complete circle around the tree or along specific areas you want to protect. Installing a partial barrier allows your tree more room to spread while still protecting vulnerable structures.

Choosing the Right Root Barrier Size

Root barriers come in different depths to suit various soil types and tree sizes. Selecting the correct size ensures effective root control for your specific situation.

• 450mm depth barriers: Suitable for smaller trees, shallow-rooted species, and well-aerated soils where most roots stay in the top 400mm
• 600mm depth barriers: The most common choice for medium-sized trees in typical garden soils with moderate drainage
• 1000mm depth barriers: Best for large established trees, compacted soils, or areas with high water tables that encourage deeper root growth

For most residential applications protecting driveways and foundations, this 450mm barrier roll provides excellent protection for smaller to medium trees in well-draining Australian soils. The 1000 micron thickness ensures durability against even aggressive root systems.

If you're dealing with larger trees or denser clay soils common in many Australian regions, the 600mm barrier option offers extra depth to redirect roots that naturally grow deeper in compacted conditions.

How to Install a Root Barrier

Installing a root barrier is straightforward and makes a manageable DIY project for most homeowners. Follow these steps for proper installation and long-lasting protection.

1. Dig a 100mm wide trench around the tree or along the areas you want to protect. You may need a 360-degree barrier around the entire tree or just a single-side barrier, depending on your tree's location and where you need to prevent root growth.
2. The depth of the trench should be between 600mm and 1000mm, depending on how aerated the soil is and the size of your tree. Very few roots grow below 1000mm depth.
3. Once you've dug the trench, insert the root barrier flat against the side of the trench wall closest to the area you're protecting. Ensure that 50mm of the barrier remains exposed above ground level to allow for soil settlement over time.
4. If placing the root barrier in a complete 360-degree circle around the root ball, use butyl tape to join each end securely. This prevents roots from finding gaps and growing through.
5. Fill in the trench with soil, compacting the dirt firmly as you go to eliminate air pockets. Proper compaction ensures the barrier stays in position.
6. Replace the lawn or alternative ground cover back over the compacted soil trench. Water thoroughly to help the soil settle.
7. Trim the barrier if needed to ensure it doesn't interfere with lawnmowers or the appearance of your garden. Make sure the top of the barrier remains slightly visible above the soil line.

When digging your trench, you'll inevitably encounter existing roots that need cutting. Use sharp tools like a reciprocating saw, loppers or a sharp spade to make clean cuts rather than tearing the roots.

Preventing Root Problems When Planting New Trees

Prevention is always easier and more cost-effective than fixing existing root problems. When planting new trees near structures, take proactive steps to manage root growth from the start.

Install root barriers at planting time to direct growth away from buildings, pipes and paved areas. This approach costs far less than retrofitting barriers around established trees or repairing damaged infrastructure.

• Choose tree species with less aggressive root systems for planting near buildings
• Plant trees at least 3-5 metres away from structures, depending on the expected mature size
• Install root barriers on the side facing structures during initial planting
• Use proper tree guards to protect young trees while directing early root development
• Avoid planting large trees directly over sewer lines or water pipes

Young trees need protection from animals, wind and equipment damage while their root systems establish. These large metal mesh guards provide excellent protection for new plantings whilst allowing airflow and light penetration, which helps the tree develop a strong trunk.

Long-Term Root Management

Root barriers made from UV-stabilised high-density polyethylene provide decades of protection when properly installed. The material resists degradation from soil chemicals, moisture and temperature extremes common in Australian conditions.

Regular monitoring ensures your root barrier continues working effectively. Check the exposed edge annually to confirm it hasn't settled below ground level where roots could grow over the top.

If you're planting multiple trees for screening, windbreaks or orchard purposes, these bulk tree guard sleeves offer cost-effective protection for large-scale plantings where you need to protect many young trees simultaneously.

A root barrier system is an effective, permanent solution to eliminate invasive root problems without removing valued trees. Our barrier products reduce damage to homes and infrastructure while keeping your established trees healthy and stable.

To find out more about invasive root prevention techniques and products, contact All Stake Supply. We'll provide expert advice and the right products for your specific root management situation. Contact us today on 1300 130 123.