Tree roots spread outward to roughly 1.5 times the tree's height, searching for water and nutrients. While this growth is natural, it turns problematic when roots grow beneath structures or into garden beds.
When roots become invasive, they can damage foundations, driveways, footpaths, retaining walls and sewer lines. This guide covers how to remove and redirect invasive roots without sacrificing an established tree.
Roots anchor a tree and draw nutrients from the surrounding soil. The taller and broader a tree grows, the wider and more aggressive its root system becomes.
Invasive roots occur when the root system extends underneath structures such as houses, footpaths, driveways or retaining walls. These roots are strong enough to lift concrete slabs, crack building foundations and push through garden walls. In garden beds, they compete with other plants for water and nutrients, often winning.
Root damage from invasive species can run into thousands of dollars in repairs. Prevention at planting time is always the best approach, but several effective options exist for regulating root growth on established trees.
Not every tree causes root problems. Some species are well known for aggressive root systems that spread far beyond the canopy and damage nearby structures. In Australia, the most common offenders include:
If you are planting near structures and want to avoid root problems, look for species with non-invasive root systems. Crepe myrtles, ornamental pears and many dwarf native varieties have compact roots that are far less likely to cause damage. Your local nursery or council can advise on suitable trees for your area.
Spotting invasive roots early can save you significant repair costs. Watch for these warning signs around your property.
If you notice any of these signs, act quickly before the damage worsens. Tree roots grow continuously, and small cracks can rapidly expand into major structural issues. Roots growing against a wall will keep pushing until the wall gives or the root is redirected.
If you suspect a tree near your home or other structure has invasive roots, act quickly before serious damage occurs. Waiting only makes 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.
For trees with roots growing above ground near your house, the first step is installing a barrier between the tree and the structure. Surface roots can then be pruned back to the barrier line, provided no more than 25% of the root system is removed at once.
Tree root control comes down to three methods: physical barriers, root pruning and ongoing monitoring. Each works best in different situations.
Physical barriers are the most reliable long-term option. HDPE root barriers installed vertically in the soil block lateral root growth entirely. Unlike concrete barriers, which crack and let roots through over time, HDPE barriers remain intact for decades.
Root pruning involves cutting back roots that have already spread into problem areas. Use sharp, clean tools and never remove more than 25% of a tree's root system in a single season. Pruning buys time but does not stop regrowth on its own. Pair it with a barrier to stop roots from growing back into the same area.
Regular monitoring catches new growth before it causes damage. Walk the perimeter of your structures each year and check for fresh root emergence, soil lifting or new cracks. Early intervention is far simpler than retrofitting a barrier around a fully established root network.
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.
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.
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.
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.
Sometimes physical barriers alone are not enough, particularly when roots have already infiltrated pipes or grown deep under a slab. In these cases, targeted root killing may be necessary.
Herbicide application: Painting a glyphosate-based product directly onto a freshly cut root surface is the most targeted approach. Cut the root cleanly, then apply within minutes while the cut is still fresh. This sends the chemical into the root system without affecting surrounding plants. Mid to late summer is the best time, as trees actively transport nutrients downward during this period.
Stump treatment: If the tree is being removed entirely, treat the stump immediately after felling to stop roots from growing back. Drill several holes into the stump and apply a concentrated herbicide. Without treatment, many species will resprout from the stump and root system for years.
Chemical methods work best alongside a physical root barrier. Kill the existing problem roots, then install a barrier to prevent new growth from reaching the same area.
Prevention is always easier and more cost-effective than fixing existing root problems. When planting new trees near structures, take 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 costs far less than retrofitting barriers around established trees or repairing damaged infrastructure.
Young trees need protection from animals, wind and equipment damage while their root systems establish. Large metal mesh tree guards provide excellent protection for new plantings whilst allowing airflow and light penetration, which helps the tree develop a strong trunk.
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 roots have been pruned or chemically treated, inspect the area each season for regrowth and treat any new shoots before they re-establish.
If you're planting multiple trees for screening, windbreaks or orchard purposes, bulk tree guard sleeves offer cost-effective protection for large-scale plantings where you need to keep young plants alive during establishment.
How deep should a root barrier be installed?
Between 600mm and 1000mm, depending on the tree size and soil type. Most tree roots grow in the top 600mm of soil, so a 600mm barrier handles the majority of residential situations. For large trees in compacted clay, go with 1000mm.
Will cutting tree roots kill the tree?
It depends on how many roots you cut and how close to the trunk. Removing more than 25% of the root system in a single season can stress or destabilise the tree. Always cut at least 1 to 2 metres from the trunk and get arborist advice for large or mature trees.
How far do tree roots spread from the trunk?
Most tree roots spread 1.5 to 3 times the height of the tree, depending on the species and soil conditions. Willows and figs can extend further, particularly when following water sources.
Can tree roots damage house foundations?
Yes. Invasive roots can crack concrete slabs, undermine footings and cause differential settlement. The risk is highest with large species planted within 3 to 5 metres of the foundation, especially in reactive clay soils that shrink and swell.
What is the best root barrier material?
HDPE (high-density polyethylene) is the industry standard. It resists root penetration, does not degrade in soil, and lasts 50 years or more. Concrete barriers crack over time and metal corrodes, making them poor long-term choices.
Can I install a root barrier myself?
Yes, for most residential situations. The process involves digging a trench, inserting the barrier and backfilling. Larger jobs around mature trees may need professional help due to the volume of root cutting involved.
A root barrier system is an effective, permanent solution to eliminate invasive root problems without removing valued trees. Browse our full range of root barrier and landscaping products to find the right option for your situation.
For advice on invasive root prevention and the right products for your project, contact All Stake Supply. Call us today on 1300 130 123 or send us a message.
