Understanding how root damage occurs, which tree species are most likely to cause it, and when tree removal is warranted helps Sydney homeowners make informed decisions about the trees on their property. Sydney Tree Company provides qualified arborist assessment and removal services across Sydney for trees causing or suspected of causing damage to buildings and infrastructure.
Root Damage Assessment by Qualified Sydney ArboristsSydney Tree Company: free quotes, Sydney-wide, 20+ years experience. Call 0431 732 265. |
How Tree Roots Cause Damage
Foundation damage
Tree roots themselves rarely crack or lift concrete foundations directly in the way that is commonly imagined. The primary mechanism of root damage to foundations in Sydney is soil moisture change. Large trees extract significant volumes of water from the soil around them, particularly during dry periods. In Sydney’s reactive clay soils, this moisture extraction causes the clay to shrink and contract, which can cause differential settlement of the soil under a building’s foundation slab. This differential settlement causes slabs to crack and buildings to develop structural movement.
Roots can also physically grow under or alongside foundations, particularly footings of older buildings, and as the root expands in diameter over many years, it can exert pressure on footings and in some cases lift or displace them. This is more common with older, shallow foundation designs.
Pipe damage
Tree root damage to pipes is a direct physical intrusion. Tree roots actively seek water, and old clay sewer pipes, which are porous and joined in short sections with mortar joints, provide an attractive source of moisture for root systems. A root that finds a gap at a pipe joint can enter the pipe and grow, progressively filling the pipe, blocking flow, and eventually breaking the pipe from inside.
Modern PVC pipes are more resistant to root intrusion because they are typically joined with rubber seals or glued connections that provide fewer entry points. However, the connections at junctions and at connection points between old clay pipes and newer PVC sections remain vulnerable.
Tree Species Most Associated with Structural Damage in Sydney
Not all trees present equal root damage risk. Species with wide-spreading, aggressive, or water-seeking root systems present higher risk to structures and pipes:
| Species | Damage risk | Notes |
|---|---|---|
| Ficus (fig) species | Very high | Extremely aggressive root systems; can cause significant structural damage over time |
| Camphor laurel | High | Common Sydney garden tree; extensive surface and sub-surface root spread |
| Liquidambar | Moderate to high | Root system extends significantly beyond canopy drip line |
| Gum trees / Eucalyptus | Variable; many species moderate to high | Root behaviour varies by species; large specimens near structures warrant assessment |
| Jacaranda | Moderate | Popular Sydney street and garden tree; risk increases as trees age and enlarge |
| Willow | High | Not common in residential Sydney but very aggressive water-seeking roots |
| Bamboo | High (for pipes) | Rhizome systems can penetrate pipe joints with considerable force |
Signs That Roots May Be Causing Damage
- Cracking in rendered or plastered external walls, particularly cracking that follows a diagonal pattern from window or door corners
- Uneven or cracked concrete paths, driveways, or paved areas near large trees
- Slow-draining or repeatedly blocking sewers that were previously functioning well
- Wet patches in the garden that were not previously present, possibly indicating a broken underground pipe
- Doors or windows that stick or no longer close correctly, particularly in older homes
Diagnosing Root Damage
Root damage can be difficult to diagnose without specialist investigation. A qualified structural engineer can assess building cracks and determine whether root-related differential settlement is the cause. A licensed plumber with a CCTV pipe inspection capability can inspect sewer pipes for root intrusion without excavation. An arborist can assess the root extension and likely root behaviour of trees on or near your property.
What to Do When Roots Are Causing Damage
Options for managing trees that are causing root damage include:
- Root barrier installation: physical root barriers installed in the soil between the tree and the structure can redirect root growth. These are most effective when installed before damage occurs and may be insufficient to stop established large root systems that are already beneath a structure
- Targeted root pruning: selective removal of roots that are directly causing or threatening a structure, undertaken by a qualified arborist. Root pruning must be done carefully to avoid destabilising the tree
- Tree removal: removal of the tree causing damage is sometimes the only practical solution, particularly for large, established trees with extensive root systems near vulnerable structures. After removal, root systems decay over several years and the risk of continued damage reduces over time
| ✦ Tree Preservation Orders and root damage: Even if a tree is causing demonstrable root damage to your property, it may still be subject to a Tree Preservation Order or local council controls that require approval before removal. Sydney Tree Company can advise on the preservation order status of trees in your area and assist with the approval process where removal is the recommended outcome. |
Frequently Asked Questions
Can I remove a tree that is damaging my property without council approval?
The ability to remove a tree without council approval depends on whether the tree is subject to a local council Tree Preservation Order or covered by provisions in your council’s Development Control Plan. Some trees above certain trunk diameter or height thresholds require council approval for removal regardless of the reason. Contact Sydney Tree Company to discuss the specific situation, and visit your council’s website or the NSW Planning Portal to check whether your tree is protected.
How far do tree roots typically extend?
Tree roots typically extend at least as far as the canopy drip line and often considerably further: root systems of established large trees can extend two to three times the canopy radius. In reactive clay soils like those common in much of Sydney, the zone of moisture influence around a large tree extends further than the root system itself, as the roots extract moisture from a wider area.