Two boundary issues land on tradies' desks constantly: who pays for the dividing fence, and how you build on flood-overlay land. Australia has no party-wall act like the UK — boundary structures run through dividing-fence law instead. Here is the framework. (Fencing law is covered here for NSW, VIC and QLD.)
Dividing fences — the equal-cost principle
The shared rule across the states: adjoining owners are equally liable (50/50) for a "sufficient dividing fence" — and whoever wants a higher standard than sufficient pays the extra, while anyone who damages the fence by negligence or a deliberate act pays the full restoration.
- NSW — Dividing Fences Act 1991: "sufficient" is judged by the existing fence, land use, privacy and what is typical locally.
- VIC — Fences Act 1968 (substantially reformed by the Fences Amendment Act 2014): mirrors the NSW principle — fences are joint property, costs shared equally.
- QLD — Neighbourhood Disputes (Dividing Fences and Trees) Act 2011: a "sufficient" fence is 0.5-1.8m high in typical materials, and the Act excludes retaining walls and walls forming part of a building from the definition of "fence".
The process for tradies:
- Serve notice first — before fencing work, give the adjoining owner a formal notice with the boundary, the proposed work and the estimated cost (NSW: a Fencing Notice; QLD: a Notice to Contribute, which must include at least one quote). This opens negotiation on type, materials and cost.
- If no agreement — escalate: NSW via Community Justice Centre mediation, then the Local Court or NCAT for a Fencing Order; QLD to QCAT if unresolved within 2 months of the notice. The tribunal sets the type, standard and cost split.
- Urgent repairs — if the fence is damaged and serving notice is impractical, an owner can do urgent work and recover half the cost afterwards.
Flood-overlay construction
On flood-prone land, the NCC (performance requirements BP1.4 in Volume 1 and P2.1.2 in Volume 2) requires the building to withstand flood pressure and movement, use water-resistant materials, and protect essential services:
- Floor levels: councils require the finished floor level above the Defined Flood Level plus freeboard — typically 300-500mm above the DFL (council-variable; the Gold Coast code, for instance, sets habitable floors at least 300mm above the DFL).
- Materials below flood level must be flood-resistant — which excludes standard plasterboard, untreated timber framing and standard electrical fittings.
- The DtS pathway is the ABCB Standard for Construction of Buildings in Flood Hazard Areas, limited to areas where the maximum water-flow velocity is 1.5 m/s or less (faster flows need specific engineering).
A flood-overlay property almost always needs a DA and often a site-specific flood assessment by a hydraulic engineer, and (in VIC) a building permit on flood-liable land needs council consent specifying minimum floor heights.
Boundary and "party" walls
Australia has no separate party-wall act (unlike the UK) — the equivalent runs through dividing-fence and common-law rules:
- A wall on the boundary line is common property of both neighbours, who share upkeep and structural responsibility; a wall entirely on one owner's land belongs to that owner.
- Building or excavating near a boundary: if your work undermines or destabilises a boundary structure or the neighbour's land, you pay the repairs — and encroachment or damage means the responsible party rectifies and compensates. The general rule: alter the land by excavation or construction near a boundary and you are liable for any destabilisation or damage.
Common mistakes
- Starting fencing work without serving the required notice (and, in QLD, without a quote).
- Treating a retaining wall as a "dividing fence" in QLD (it is excluded).
- Using standard plasterboard or untreated framing below the flood level.
- Excavating near a boundary and destabilising the neighbour's wall or land.
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