Earlwood 2206 · Canterbury-Bankstown
Duplex Builder in Earlwood: Attached or Fully Detached?
One shared wall, or none at all? Earlwood owners ask me that first.
Earlwood's 1920s to 60s homes sit on blocks of 500 to 800 square metres running down towards the Cooks River. Plenty of them can carry two dwellings. The first real design decision is whether those two homes share a wall or stand apart, and it changes the cost, the approvals and what buyers will pay.
Short answer
Attached or detached duplex in Earlwood: which is better?
Attached is usually cheaper and fits narrower lots, but the shared wall must be fire-rated and meet sound-insulation rules, often as two separate leaves with a gap. Detached homes avoid that wall and can resell better, but need more width for side setbacks. Earlwood's slope and Cooks River flood areas also matter. Building here costs about $2,530 to $3,050 per m² for a mid-range finish.
Written and reviewed by Oliver Alameri
Licensed builder, NSW Contractor Licence 487805C · Founder, Buildana
Fact-checked
What the shared wall actually has to do
An attached duplex is two Class 1 dwellings joined by a separating wall. Under the National Construction Code that wall has to stop fire spreading from one home to the other, which means a fire-resistance level of 60 minutes, and it has to run right up to the underside of the roof so there's no gap in the ceiling space.
It also has to stop sound. The code sets a minimum airborne sound rating for walls between dwellings, and where a bathroom or kitchen on one side backs onto a living room or bedroom on the other, the wall needs discontinuous construction so vibration doesn't carry through. In practice that's two separate leaves with a gap between them.
A builder who does this regularly finds it routine. It's still a real cost, though, and it's the line cheap duplex quotes most often skimp on. Neighbours who can hear each other's shower at 6am don't stay happy.
- Fire-rated separating wall carried to the roof
- Sound rating that meets the code between dwellings
- Discontinuous construction where wet areas meet habitable rooms
- Separate services, meters and connections for each home
You can hear a cheap party wall. So can the next owner at the open house.
Going fully detached
A detached dual occupancy is two free-standing houses on one lot. No shared wall, so no separating wall. Instead each home needs its own external walls all round, and the gap between them has to meet the fire separation rules in the building code, including limits on openings close to the boundary between them.
More external wall and roof edge means more cost per square metre. What you get back is two houses that feel like houses. No shared wall to hear through, easier to insure and maintain independently, and, for many buyers in a suburb like Earlwood, a stronger sale price.
Detached works best on wider lots. On a narrow block, the side gaps can eat so much width that each home becomes a corridor. That's why we test both layouts on your actual survey before recommending one.
Two homes on your Earlwood lot?
Send the address and a survey if you have one. I'll test an attached and a detached layout against your lot, then price each so you can compare.
0476 300 300Earlwood's slope and the Cooks River
Much of Earlwood falls towards the river, and on a sloping lot a front-and-back detached layout can step with the land. The rear home sits lower, keeps its view and gets a private garden. The front home owns the street.
Lots near the Cooks River may carry flood mapping, and a few streets have heritage or character controls. The Canterbury-Bankstown planning controls set the minimum lot size and frontage for dual occupancy, and state rules may also apply. The planning certificate settles that before any design work.
Many original houses here are 1920s to 60s brick. Fibro sleep-outs and old paint are the usual suspects, so asbestos and lead testing goes in before demolition is priced.
Cost and resale
Using Rawlinsons for Sydney with Earlwood's 1.15 adjustment, a mid-spec build runs about $2,530 to $3,050 a square metre. Attached saves on external wall and roof. Detached adds it back, plus a bit more for services running to two separate buildings.
Which pays better depends on the lot and the buyers. On a wide, deep block with a slope, detached often wins at sale. On a narrower lot, a well-built attached duplex gives each home a better floor plan. We put both on paper with numbers.
Attached or detached: six questions
Answer these for your Earlwood lot and the right layout usually becomes obvious.
- 01
Frontage and depth from the survey, not the listing
- 02
Which way the lot slopes, and how steeply
- 03
Minimum lot size and frontage under the current dual occupancy controls
- 04
Flood or heritage notes on the planning certificate
- 05
Selling one home, both, or keeping them
- 06
How much each option costs to build, side by side
Earlwood duplex questions
What is a detached duplex?
Two free-standing homes on one lot, with no shared wall. Planning calls it a detached dual occupancy. Each home has its own walls and roof, and the gap between them must meet the building code's fire separation rules.
Is an attached or detached duplex cheaper to build?
Attached is usually cheaper per square metre because the homes share a wall and less external envelope is needed. Detached costs more but can sell for more on the right lot.
Does the wall between attached homes need to be fire rated?
Yes. The separating wall between two Class 1 dwellings needs a fire-resistance level and must extend to the underside of the roof. It also needs to meet sound insulation requirements.
Will my Earlwood block take two dwellings?
Many Earlwood lots qualify, subject to lot size, frontage and the current Canterbury-Bankstown and state controls. A survey plus the 10.7 certificate confirms it.
Sources and references
Costs are from the Rawlinsons handbook with the local cost index applied; rules and timeframes are checked against the sources below.
Shared wall or none. Decide it on numbers.
An Earlwood duplex designed around your lot, your slope and your plans for selling or keeping.