In short
Since 1 January 2024, the Urban Forest Act 2023 protects any private tree 8 m or taller, with a canopy 8 m or wider, or a trunk 1 m or more around at 1.4 m, plus every tree on public land, including verge trees. Inside a protected tree's zone, digging deeper than 100 mm over 4 m² or more is prohibited groundwork unless approved. Plan footings around it.
Key takeaways
- The Urban Forest Act 2023 replaced the Tree Protection Act 2005 on 1 January 2024, with lower size thresholds.
- The protection zone is the canopy area, plus a 2 m band around the canopy, plus 4 m around the trunk.
- Inside the zone: no root damage, no compacting more than 10% of it (a slab counts), and no digging or filling more than 100 mm over 4 m² or more.
- A neighbour's protected tree counts too. Tree management plans are compulsory in a DA or BA where a protected tree may be affected.
- Engineering answers include piers, suspended floors and beams that bridge over root areas.
Which trees are protected in the ACT?
A tree on private land is protected if it passes any one of six tests, and every tree on public land is protected, including the verge tree outside your house. The tests come from the Urban Forest Act 2023, which replaced the Tree Protection Act 2005 on 1 January 2024.
| Test | Protected if |
|---|---|
| Height | 8 m or taller |
| Canopy | 8 m or wider |
| Trunk | Circumference of 1 m or more, measured 1.4 m above natural ground |
| Listed | On the ACT Tree Register (a registered tree) |
| Dead native tree | Circumference of 1.88 m or more at 1.4 m |
| Canopy contribution | Planted in the last 5 years under a canopy contribution agreement |
| Public land | Every tree, including verge trees |
Not protected: dead non-native trees and declared pest plants. Source: ACT City Services; Urban Forest Act 2023.
A quick trunk check
Wrap a tape around the trunk at 1.4 m above the ground. If it reads 1 m or more, the tree is protected whatever its height. A trunk 1 m around is only about 32 cm across.
What is a tree protection zone?
It is the ground around a protected tree where building work is restricted. ACT City Services defines it in three parts, and the zone is all of them together.
| Part of the zone | How far it reaches |
|---|---|
| Under the canopy | The whole area beneath the branches |
| Around the canopy | A 2 m band beyond the canopy's outline on the ground |
| Around the trunk | A 4 m band around the trunk, measured at 1 m above the ground |
| Or, instead | The area set in an approved tree management plan |
Illustrative example: a eucalypt with a round canopy 10 m across, centred on the trunk, has a zone reaching about 7 m from the trunk on every side: 5 m of canopy plus the 2 m band. That can take in part of the house, the driveway or the neighbour's yard.
What building work is banned inside the zone?
Four kinds of "prohibited groundwork" under section 15 of the Act, and most building work involves at least one of them. Each limit keeps its condition, so read them closely.
| Prohibited groundwork | The limit | Building work it catches |
|---|---|---|
| Damaging roots | Any damage to the tree's roots | Trenches for footings, drains and services |
| Compacting soil | Over 10% of the zone; the examples include a concrete slab, heavy vehicles, stored materials and a shipping container | A slab on the ground, a driveway, site parking, stockpiles |
| Excavating | Deeper than 100 mm over 4 m² or more | Strip footings, slab set-downs, pools, cuts for retaining walls |
| Raising soil | More than 100 mm over 4 m² or more | Fill pads, raised garden beds, levelling a yard |
Urban Forest Act 2023, s 15. ACT City Services says penalties can reach $80,000 for an individual and $405,000 for a corporation.
What approval do you need to build near a protected tree?
Work on or near a protected tree needs permission: a tree activity application, or a tree management plan lodged through your development approval (DA) or building approval (BA). That applies even when the tree is on the neighbour's block.
- Tree management plans are now compulsory in DA, BA and driveway approvals where a protected tree may be affected.
- Bonds can be required.
- Exempt work loses its exemption if it would breach the Urban Forest Act. A carport or deck that needs no DA elsewhere can need approval near a protected tree.
- Removing a protected tree means planting 2 trees, or paying $600 for each tree not replanted.
We don't do arborist assessments, and we can't promise any tree will be approved for removal. Our part is the structure: footings and floors designed to work within the zone and the conditions your approval sets.
How do you check a project against a protected tree?
In five steps, before the design is fixed. Doing them early is what keeps a tree from redrawing the plans halfway through approval.
Measure the trees
Every tree within reach of the work, including the neighbour's and the verge trees: height, canopy width and trunk circumference at 1.4 m.
Draw the zones
Mark each protected tree's zone on the site plan: the canopy area, a 2 m band around it and 4 m around the trunk.
Test the work
Check footings, slabs, trenches, fill and site access against the four groundwork limits above.
Plan the approval
Where a protected tree may be affected, a tree management plan goes into the DA or BA. Your designer or certifier confirms what is needed.
Design the footings
Footings and floors are designed to work within the limits the approval sets.
How do engineers design footings near a protected tree?
By reducing digging, filling and compaction inside the zone, and by putting the structure's weight where the roots aren't. The approved tree management plan sets the limits; the footing design works inside them.
Piers in place of strip footings
A few small excavations, positioned with the plan, in place of a continuous trench through the root area.
Suspended floors
A floor on piers over the zone, in place of a slab on the ground that would compact it and need a set-down.
Bridging beams
Beams that span across a root area, carried on footings outside it or at its edge.
A layout that steps around
Moving or reshaping the extension, carport or driveway so less of it sits in the zone.
Trees also draw water from clay soils, so the ground near a big tree moves more as the seasons change. That affects how deep and stiff the footings need to be. Footing and slab design starts at $1,290 + GST ($1,419 inc GST), with any soil test arranged at cost.
Is a tree cracking my house?
It can be. Tree roots draw moisture from the clay under one side of a house, the clay shrinks, and that side settles. Leaks, poor drainage and seasonal swelling can add to it, and most movement has more than one contributor.
What moves a house? Four common causes
- Trees and roots draw moisture from the soil near a footing, so clay under that side shrinks.
- Reactive clay swells when wet and shrinks when dry, moving footings with the seasons.
- Leaking pipes or poor drainage soak and soften the ground under part of the house.
- Poorly compacted fill keeps settling under a footing long after the house is built.
Canberra's weather makes it harder to read. Canberra Airport had 359 mm of rain in 2019 and 913 mm in 2021, so clay under homes has been drying and wetting hard. Our guide to cracks in walls in Canberra explains how to tell the causes apart.
We found no ACT legal rule on claims for damage from tree roots, so we stick to the engineering. A cracks and footing movement report finds the cause and says what to do about it, from $1,090 + GST ($1,199 inc GST).
When should you call a structural engineer?
Before the design is fixed, if a protected tree, yours or a neighbour's, sits within a few metres of the work. The tree management plan and the footing design need to agree, and both go into the same approval.
- New footings or a slab near a tree: footings, slabs and site classification.
- An extension towards a tree: extension and renovation engineering, a fixed quote from your plans.
- A rebuild on a block with a protected tree: knock-down rebuild engineering.
- Cracks near a tree: a cracks and footing movement report.
We're engineers only: we don't remove trees, build or recommend contractors, so our advice isn't tied to what you buy next. Send plans and a photo of the tree, add up to 5 files, and we reply with a fixed quote in under 20 minutes on average, during business hours. Prices are the same across every Canberra district.
Building near a big tree?
Send your plans and a photo of the tree for a fixed quote in under 20 minutes on average, during business hours.
Sources
- Urban Forest Act 2023 (A2023-14), ACT Legislation Register. Sections 15 and 17; republication in effect 2 January 2026
- ACT City Services, Tree protection laws. Accessed 6 November 2026
- ACT Government, Check if you need a DA. General criteria for exempt work; accessed 6 November 2026
