How much does it cost to build a duplex in Sydney?
As an indicative 2026 range, a duplex (two attached homes) in Sydney costs about $3,000 to $3,500 per m² at standard finish, $3,600 to $4,400 at mid finish and $4,800 to $6,200 at luxury finish, excluding GST.
Price yours in the calculator Get a fixed priceA duplex is two homes side by side on one lot, with a fire-rated wall between them. It is a light build, the same construction as a house, so the rate per square metre sits close to a knockdown rebuild; you get two homes for the money and share the slab, roof and site works between them. Most Sydney duplexes are two storeys of about 140 to 200 m² a side, built in 10 to 14 months.
Sydney rates, 2026
| Finish | Per m² of floor area | For 300 m² | Per home |
|---|---|---|---|
| Standard project-home specification | $3,000 to $3,500 | $900k to $1.05m | $450k to $525k |
| Mid where most owner-occupier work lands | $3,600 to $4,400 | $1.08m to $1.32m | $540k to $660k |
| Luxury architect-detailed, bespoke joinery | $4,800 to $6,200 | $1.44m to $1.86m | $720k to $930k |
Excluding GST. The 300 m² example is 2 homes, gross floor area across all levels, garages and balconies excluded.
What the three levels of finish mean for duplex
Standard
Project-home plans and a builder's range of finishes: laminate kitchens, tiled wet areas, aluminium windows. What the volume duplex builders quote.
Mid
A designed pair rather than a mirrored plan: stone benches, engineered timber, better glazing and joinery, a landscaped front. Where most owner-occupiers land.
Luxury
Architect-detailed, bespoke joinery, high-performance glazing, imported stone, often a basement or a lift on a sloping block.
Worked examples
| Floor area | Standard | Mid | Luxury |
|---|---|---|---|
| 240 m² | $720k to $840k | $864k to $1.06m | $1.15m to $1.49m |
| 300 m² | $900k to $1.05m | $1.08m to $1.32m | $1.44m to $1.86m |
| 400 m² | $1.20m to $1.40m | $1.44m to $1.76m | $1.92m to $2.48m |
Build cost only, excluding GST and the items below. Run your own floor area through the calculator.
What drives the number
- The site: a sloping block, rock, poor soil or a battle-axe driveway adds 8 to 15% before the frame goes up.
- Two of everything: two kitchens, two sets of bathrooms, two meters and two driveways, which is why the rate stays near a single house even though the walls are shared.
- The fire wall and acoustic separation between the homes, and the fire rating on anything near the boundary.
- Subdivision: Torrens title for each half (survey, plan registration, council contributions) is outside the build cost and runs into tens of thousands.
On top of the build
- Demolition of the existing house: about $40k to $70k.
- A steep or difficult site: add about 8% to 15%.
- Bushfire construction on bushfire-prone land: add about 3% to 6%.
- Not included: GST, design and council fees, connections and contributions, landscaping, finance and holding costs.
Which kind of duplex is yours?
The simplest and cheapest: two mirrored homes, one street frontage each.
A shared driveway, a rear home with less street appeal, more site works.
Excavation, retaining and waterproofing add a step to the rate.
Owner-occupiers who sell one side and keep the other usually spend more on their own half.
Individual facades, custom joinery, high-performance envelope.
What these look like
Design studies, not Estier projects.
Questions people ask
What does a 300 m² duplex cost to build in Sydney?
About $900,000 to $1.05m at standard finish, $1.08m to $1.32m at mid and $1.44m to $1.86m at luxury in 2026, excluding GST, demolition and subdivision. That is for both homes together, about 150 m² each.
Do I need an 800 m² block for a duplex?
It depends on the council and whether the block is in the state low and mid-rise area. Many councils set 800 m² and a frontage minimum outside it; inside it the state rule is 450 m² and 12 m. Run the address through Block Checker to see which applies.
Can I keep one half and sell the other?
Yes, once the two homes are on separate titles. Torrens subdivision needs a survey, a plan registration and usually council contributions, which are extra to the build cost.
How long does a duplex take to build?
Ten to fourteen months on site for a two-storey pair, after a design and approval period of four to nine months depending on whether it goes as complying development or a DA.
Is a duplex cheaper per home than two houses?
Usually by 10 to 20%: the slab, roof, scaffold, site works and one shared wall are split between two homes, and the land is bought once.
Before you price it
Make sure the block can take it. Can your block take a duplex? Check it on Block Checker — enter the address and see the lot, the zone and what it can carry under the rules today.
Want the real number?
These are planning ranges, not a quote. Estier designs and builds in Sydney and gives a fixed price against a drawn scheme. Send the brief.
Other Sydney build costs: New house · Terraces · Manor house · Granny flat · Apartments · Renovation
Indicative only. Rates are built off the RLB Riders Digest (Sydney, 2026 edition) and cross-checked against current Sydney builder pricing. They are a planning range, not a quote.