Can Tree Roots Damage My House Foundation?

Yes, tree roots can damage house foundations, sewer pipes, retaining walls, and driveways — but the extent of the risk depends on the tree species, soil type, proximity to structures, and the condition of the infrastructure itself. Not every tree near a house is a problem, but certain species in certain soils are responsible for the majority of root-related structural damage on the Central Coast and across Sydney.

I'm Daymian McGovern, and as a certified arborist with over 13 years of experience, root damage assessments are one of the most common callouts I get. Here is a practical guide to understanding the risk, spotting the signs, and knowing when to act.

How Tree Roots Interact with Structures

Tree roots do not bore through concrete or masonry like drills. What they actually do is more subtle and, in some ways, more damaging over time:

Direct Mechanical Pressure
Large structural roots grow in diameter each year. When a root is growing against a foundation wall, retaining wall, or pipeline, the incremental pressure can crack, displace, or deform the structure over years. This is most common with large, vigorous species planted too close to buildings.

Soil Moisture Changes (Subsidence)
This is the bigger issue, particularly on the Central Coast's reactive clay soils. Tree roots extract large volumes of water from the soil. In clay soils, this causes the clay to shrink, which leads to differential ground movement — one part of the foundation settles while another does not. The result is cracking in walls, uneven floors, and doors or windows that stick.

During drought periods, this effect is amplified. I see a significant increase in root damage callouts across the Central Coast after dry summers, particularly in areas with heavy clay like parts of Wyoming, Narara, and West Gosford.

Pipe Infiltration
Tree roots are attracted to the moisture and nutrients around sewer and stormwater pipes. They enter through existing cracks or joints in older clay and concrete pipes, then grow inside the pipe, eventually blocking it. PVC pipes with welded joints are much more resistant, but older properties — and there are plenty across the Central Coast, Lake Macquarie, and the North Shore — often still have clay or earthenware pipes underground.

Worst Offender Species on the Central Coast

Not all trees are equal when it comes to root damage. Based on my experience working across the region, these species cause the most problems:

High Risk
- Figs (Ficus species) — Port Jackson fig, Moreton Bay fig, and rubber trees have incredibly aggressive, wide-spreading root systems. They are the single biggest source of root damage I encounter.
- Camphor Laurel (Cinnamomum camphora) — extremely common across the Central Coast as legacy plantings. Massive, shallow root systems that lift driveways and paths.
- Coral Trees (Erythrina species) — fast-growing with invasive surface roots.
- Liquidambar — popular street and garden tree with roots that aggressively seek out pipes and foundations.

Moderate Risk
- Large Eucalyptus species — spotted gum, Sydney blue gum, and flooded gum can cause subsidence on clay soils due to high water uptake, though their roots are less mechanically aggressive than figs.
- Jacaranda — can cause pipe intrusion and surface root issues when planted close to structures.
- Willow (Salix species) — extremely water-hungry; a serious threat to any drainage infrastructure nearby.

Lower Risk
- Most native understorey species — banksias, grevilleas, and smaller native trees rarely cause structural issues.
- Palms — fibrous root systems that generally do not damage structures (though Cocos palms can crowd foundations if planted tight against walls).

Warning Signs of Root Damage

If you notice any of the following, it is worth investigating whether tree roots are contributing:

Foundation and Structural Signs
- Diagonal cracks in brick walls, especially stepping cracks along mortar joints
- Cracks widening at the top — indicates differential settlement, often root-related subsidence
- Doors and windows sticking or not closing properly
- Uneven or sloping floors
- Gaps appearing between walls and ceilings or walls and floors

Pipe and Drainage Signs
- Slow draining sinks, showers, or toilets — especially if getting progressively worse
- Gurgling sounds from drains
- Recurring blockages despite clearing
- Damp patches in the yard near sewer or stormwater lines
- Sinkholes or soft spots in the lawn above pipe routes

Surface Damage Signs
- Lifted or cracked driveways, paths, and pavers
- Visible surface roots pushing up against structures
- Retaining walls leaning or cracking

Solutions: What Can You Do?

The right solution depends on the severity of the problem and whether the tree is worth retaining.

Root Barriers

For trees you want to keep, a root barrier can redirect root growth away from structures. This involves:

- Excavating a trench between the tree and the structure
- Installing a purpose-made root barrier (typically a high-density polyethylene panel) to a depth of 600mm–900mm
- Pruning any roots found in the trench on the structure side

Root barriers work best as a preventive measure or when root intrusion is still in its early stages. They are not effective once major roots are already established under a structure.

Root Pruning

Selective root pruning — cutting specific roots that are causing the problem — can be effective for surface root issues like lifted paths and driveways. However, it must be done carefully. Removing too much of a tree's root system can destabilise it, creating a whole different safety risk.

As a general rule, I avoid cutting roots within the Structural Root Zone (SRZ) — the area close to the trunk where roots provide essential stability. The SRZ radius varies by species and trunk diameter.

Tree Removal

Sometimes the tree has to go. If a tree is causing significant foundation damage, recurring pipe blockages, or is simply too close to a structure for any barrier to be effective, tree removal followed by stump grinding is the most definitive solution.

After removal, existing root decay takes several years. If you are concerned about ongoing subsidence effects, your structural engineer may recommend rehydrating the soil gradually to allow it to re-swell in a controlled manner.

Pipe Relining or Replacement

If tree roots have infiltrated your sewer or stormwater pipes, you will need a plumber to clear the roots and reline or replace the damaged section. I work alongside plumbers regularly — they clear the pipe, I address the tree, and together we solve the problem permanently.

When to Act

My advice is straightforward: act early. Root damage is progressive. A small crack today becomes a major structural problem in two or three years. If you have a large tree within 5–8 metres of your house — especially one of the high-risk species listed above — and you are seeing any of the warning signs, it is worth getting an arborist assessment.

I provide root damage assessments across the Central Coast, Lake Macquarie, Newcastle, the North Shore, and the Hills District. The assessment includes identifying the species, evaluating root architecture, and recommending the most appropriate solution — whether that is a barrier, selective root pruning, tree pruning to reduce canopy and water demand, or removal.

Concerned About Tree Roots Near Your Home?

Call me on 0432 687 647 or reach out through our contact page for a root damage assessment. I will inspect the tree, evaluate the risk to your property, and give you clear options — no scare tactics, just honest advice from a certified arborist who has seen it all across the Central Coast.