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Can I build a duplex (dual occupancy) in Brisbane?

A duplex is a 'dual occupancy' — two dwellings on one lot. Whether your block qualifies comes down to the Brisbane City Plan minimum site area for your zone, which is large in low-density areas. Here's what's required, plus a free way to test it.

Brisbane owners and small investors weighing a duplex / dual occupancy for rental yield or to live in one and rent the other.

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Dual occupancy — always a development application

Two dwellings on one lot is a 'dual occupancy' under the Brisbane City Plan Dual Occupancy Code (9.3.6). Unlike a single house or a granny flat, a dual occupancy is always assessable development — it always needs a development application. Whether it's a straightforward one comes down to your zone and, above all, your site area.

Minimum site area by zone (Table 9.3.6.3.B)

This is where most duplex ideas live or die. In the Low density residential zone the minimum site for a dual occupancy is a substantial 3,000 m² with 40 m frontage — duplexes there are for large lots only. The realistic zones are Low-medium density and Character (Infill housing):

Low density residential — 3,000 m² site, 40 m frontage (large lots only)
Low-medium density residential — 600 m² site, 15 m frontage
Character residential (Infill housing precinct) — 800 m² site, 20 m frontage
Maximum height 9.5 m / 2 storeys (or 11.5 m / 3 in the up-to-3-storey precincts)
Maximum building footprint (site cover) 50%; combined building length ≤ 25 m
Private open space for each dwelling; on-site parking per dwelling

What it means for your block

If you're in a standard low-density suburb on an ~600 m² block, a dual occupancy generally isn't supported — the zone wants 3,000 m². If you're in a Low-medium density or Character Infill area, an ordinary block can work. Either way it's a development application; meeting the Table B site area and the height/footprint outcomes makes it a clean code-assessable case rather than a hard merit argument.

Check your plans against the rules — free

Have a concept or plans? The free Brisbane plan compliance check reads the site area, frontage, height and footprint off your PDF and tests them against the Dual Occupancy Code — telling you whether it meets the Acceptable Outcomes or needs a performance-based case. For the full feasibility write-up, the DA Feasibility report covers the pathway and supporting analysis.

Real example

Worked example

A 650 m² Low-medium density block (16 m frontage) suits a 2-storey dual occupancy at ≤ 9.5 m and ≤ 50% site cover — a code-assessable DA. The same duplex proposed on a 650 m² Low density block fails the 3,000 m² site-area outcome and would be a difficult merit case.

The statutory basis

Dual occupancies in Brisbane are assessed under the Brisbane City Plan 2014 Dual Occupancy Code (section 9.3.6), made under the Planning Act 2016. The minimum site areas are Table 9.3.6.3.B; a neighbourhood plan can vary them, so confirm the controls for your address.

Brisbane City Plan 2014 — Dual Occupancy Code

Section 9.3.6 (AO1, Table 9.3.6.3.B)

Planning Act 2016 (Qld)

Assessable development — dual occupancy

Planning Regulation 2017 (Qld)

Definition — dual occupancy

Frequently asked questions

Can I build a duplex on a 600 m² block in Brisbane?

Only if it's in the Low-medium density residential zone (600 m² minimum) or Character Infill (800 m²). In the Low density residential zone the minimum is 3,000 m², so a duplex on a standard 600 m² low-density block isn't supported.

Do I need a DA for a dual occupancy in Brisbane?

Yes — always. A dual occupancy is assessable development, so a development application is required regardless of the zone. Meeting the Table B site area and the height/footprint outcomes keeps it a straightforward code-assessable application.

What's the difference between a duplex and a granny flat?

A duplex (dual occupancy) is two equal dwellings and always needs a DA. A granny flat (secondary dwelling) is subordinate to a main house, capped at 80 m², and can be accepted development without a DA if it meets the rules.

Can I subdivide a duplex and sell the halves?

Potentially, via a separate reconfiguring-a-lot application, but the resulting lots must meet the subdivision minimum lot sizes — so it depends on the site. The duplex DA and the subdivision are separate approvals.

How tall can a duplex be?

Generally 9.5 m and 2 storeys, rising to 11.5 m and 3 storeys in the up-to-3-storey precinct of the Low-medium density zone.

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