Service
Duplex and dual occupancy builders
Two dwellings on one site — to live in one and rent or sell the other, or to develop.
When this is the right path, and when it is not
Your block meets the lot size and frontage rules and the zoning permits a second dwelling.
It is not viable where minimum lot size or frontage falls short, and it is a harder project where a character or heritage control applies.
How the job actually runs
- 01Test whether the site permits it
Zone, minimum lot size and frontage decide this, and they vary by council and by address. It is the first question, not a detail.
- 02Decide torrens, strata or neither
Whether the dwellings can be separately titled changes the finance, the sale value and the planning path. Settle it before design.
- 03Design for two, not one twice
Party walls, acoustic separation, separate services and independent access are the things that make a duplex work or fail.
- 04Get the feasibility done properly
A duplex is a small development. Treat it with development discipline — costs, timelines, finance and exit — not house-building optimism.
Where these jobs go wrong
The four things that most often cost people money on a duplex and dual occupancy job specifically.
- Assuming the block qualifies
Minimum lot size and frontage rules rule out most blocks. Confirm against the address before you spend money on anything.
- Forgetting the subdivision is a separate process
Building two dwellings and being able to sell them separately are different things with different approvals and different timeframes.
- Under-specifying the party wall
Acoustic and fire separation is regulated and it is the thing occupants complain about. It is not a place to save.
- Ignoring the finance structure
Lenders treat dual occupancy differently to a single house. Talk to a broker before you commit to a build contract.
What moves the price
No figures — a number without your site and your specification is a guess. For a duplex and dual occupancy job, these are what actually move it.
- Party wall construction and acoustic rating
- Separate service connections and metering
- Site coverage and landscaping requirements
- Torrens versus strata subdivision costs
- Driveway and parking arrangement
- Council contributions
Where we cover this, and what the planning data says
Typical height limit is the control that most often decides how a duplex and dual occupancy job runs. Read from state planning data.
| Suburb | Council | Typical height limit |
|---|---|---|
| Balmain | Inner West Council | not mapped |
| Leichhardt | Inner West Council | not mapped |
| Marrickville | Inner West Council | 9.5m |
| Parramatta | City of Parramatta Council | 11m |
| Westmead | City of Parramatta Council | 11m |
| Nundah | Brisbane City Council | not mapped |
| Collinswood | City of Prospect | not mapped |
| Nailsworth | City of Prospect | not mapped |
Suburb-level, read from state planning data. Not a report on any individual block.
What to ask a builder about a duplex and dual occupancy job
Specific to this kind of job. The general list is in questions to ask a builder.
- Does this block meet the minimum lot size and frontage for a dual occupancy?
- Will it be torrens, strata or community titled, and when does that happen?
- Have you built a duplex under this council, and what did they push back on?
- How are the party wall, acoustic separation and fire rating detailed?
- If I am selling one side, what does the contract say about staging and access?
Related
Questions people ask
What is the difference between a duplex and a dual occupancy?
The terms are used loosely and differ by state. Broadly a duplex is two attached dwellings; dual occupancy can be attached or detached. What matters is what your council's controls actually permit.
Can I sell one and keep the other?
Only if the site can be subdivided, which is a separate approval to the building permit. Establish that first — it determines whether the project makes sense.
Do I need a builder who has done duplexes?
Strongly recommended. Party walls, dual services and staged occupancy are where inexperience costs money.
Duplex and dual occupancy builders near you
Tell us about the job and where it is. We'll find builders who do this specific work in your suburb — or say plainly that we can't yet. Free to you: the builder pays us, and only if you sign.
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