Dual occupancy design in Sydney starts with the block, not the floor plan. Lot width, lot area, zoning and what your council allows for subdivision decide whether two homes will fit, and those answers are available before any drawing is done.
Dual occupancy design in Sydney starts with the block, not the floor plan. Lot width, lot area, zoning and what your council allows for subdivision decide whether two homes will fit, and those answers are available before any drawing is done. This guide covers what a block needs, the layout options, how approval works, and what a designer for a dual occupancy is responsible for.
What counts as a dual occupancy
A dual occupancy is two dwellings on one lot. It can be attached, with the homes sharing a wall or stacked, or detached, with two separate buildings. "Duplex" is the everyday word for the attached, side by side version.
It is a different thing from a granny flat. A secondary dwelling is limited in size and cannot be sold separately from the main house. A dual occupancy produces two full-sized homes, and where council allows, each can be subdivided onto its own title.
Where dual occupancies are allowed
The rules widened in recent years. State housing reforms that began in mid 2024 made dual occupancies permissible with consent in low density residential zones across most of NSW, including council areas that had previously prohibited them.
Permissible does not mean approvable on every lot. Each council's local environmental plan still sets minimum lot sizes and other standards, and some land is excluded on bushfire, flood or heritage grounds. Controls have changed more than once, so check the current position on the NSW Department of Planning site or with council before buying a block on the strength of last year's rules.
What your block needs
Before spending anything on design, test the site against these:
- Zoning. Confirm dual occupancy is permitted in your zone.
- Lot area. Councils and the State code set a minimum, and it varies by area.
- Frontage. Side by side designs need enough width for two entries, two garages and side setbacks. Narrow lots usually cannot do it.
- Slope. A cross fall complicates a shared wall and driveway levels.
- Corner or rear lane access. Either one makes a good layout far easier.
- Constraints. Heritage, bushfire, flooding, easements and significant trees.
- Services. Sewer and stormwater location affects where buildings can sit.
A Section 10.7 planning certificate and a detail survey answer most of this. The exact numbers for your lot are the first thing we check on any dual occupancy design enquiry.
Layout options
Side by side. Two homes facing the street, sharing a central wall. Both get a street address and a backyard. Needs width.
Front and back. One dwelling behind the other with a driveway down the side. Works on narrower, deeper lots. The rear home has less street presence and the driveway takes land.
Corner lot. Each dwelling faces a different street. Often the best outcome: separate entries, no shared driveway and good privacy.
Detached. Two freestanding houses. More building cost and more site coverage, with better separation.
Approval: DA or CDC
Both pathways can apply. A complying development certificate is available where the lot and design meet every standard in the State's low rise housing code, which sets its own minimum lot dimensions. A development application to council is needed where the site is excluded or the design varies a control.
Because dual occupancies carry more planning risk than a single house, the pathway question should be settled first. We cover the comparison in more detail on our DA and CDC documentation page. Applications are lodged through the NSW Planning Portal.
Subdivision is a separate question
Getting two homes approved does not mean you can sell them separately. Subdivision, whether Torrens title or strata, depends on the minimum lot size in your council's plan and needs its own approval.
Decide the end goal at the start. A design intended to be subdivided has to account for separate services, fire separation between the dwellings, individual drainage and compliant lot boundaries. Retrofitting those later is costly, and sometimes not possible.
What drives dual occupancy design cost
We do not quote design or build prices without a site, and nobody credible can. The drivers are:
- Site slope and the amount of excavation or retaining.
- Attached or detached form.
- Two kitchens, multiple bathrooms and two sets of services.
- Fire and acoustic separation at the shared wall.
- Driveway, stormwater and any on-site detention.
- DA or CDC, and the consultant reports each needs.
- Subdivision costs, council contributions and utility connections.
- The level of finish, which should match the local market.
The honest caveat: a dual occupancy is not a guaranteed profit. Council contributions, holding costs and construction prices can absorb the margin, particularly where the finished homes will not sell for much more than the original house would. Have the numbers checked by someone independent before you commit.
What a designer for a dual occupancy does
LCG Architects designs, documents and obtains approval. We do not build. On a dual occupancy that covers:
- a feasibility check of the lot against current controls
- concept design for both dwellings
- coordinating the surveyor, engineer, stormwater designer and other consultants
- DA or CDC documentation
- construction drawings that builders can price accurately
The design has to make two homes feel separate on one lot. Privacy between the dwellings, sunlight to both living areas and two entries that do not look like an afterthought are what a buyer or tenant notices.
Next step
Send us the address. We will check the zoning, lot dimensions and constraints and tell you whether a dual occupancy is realistic on that block and which layout it favours.
Common questions
What is the minimum lot size for a dual occupancy in Sydney?
It depends on the council and the approval pathway. Each local environmental plan sets its own minimum lot area, and the State complying development code has separate lot size and width requirements. The figure for your block should be confirmed from the current plan before design starts.
Can I subdivide a dual occupancy?
Sometimes. Subdivision is controlled by the minimum lot size in your council's local environmental plan and requires separate approval. Some councils allow Torrens or strata subdivision of dual occupancies and others restrict it. Confirm this before design, because it changes how the dwellings are serviced and separated.
Is a duplex the same as a dual occupancy?
A duplex is one type of dual occupancy. Planning law uses "dual occupancy" for any two dwellings on one lot, attached or detached. "Duplex" usually refers to two attached homes side by side sharing a common wall.
How long does dual occupancy approval take?
A complying development certificate can be issued within weeks once a complete application is lodged. A development application commonly takes several months. Design and documentation before lodgement adds further time, particularly where several consultant reports are needed.
Do I need an architect for a dual occupancy?
There is no legal requirement to use an architect for a dual occupancy. An architect or experienced building designer is worth using because lot constraints, privacy, fire separation and subdivision requirements all have to be resolved in one design. Poor resolution at this stage is expensive to fix during construction.