Ashfield 2131 · Inner West Council
Duplex Builders in Ashfield: Does Your Lot Qualify for CDC?
A duplex in Ashfield without a DA? Maybe. Check three things first.
Complying development can get a duplex approved in weeks rather than months. In Ashfield, plenty of people ask about it, and plenty of lots don't qualify. Heritage areas, small blocks and narrow frontages rule many out. Here's how to know where yours stands before anyone draws a line.
Short answer
Can I build a CDC duplex in Ashfield?
Only if the lot passes three tests: it isn't in a heritage conservation area, it meets the minimum lot size, and it has the required frontage. If it qualifies, a certifier can approve a code-compliant duplex within a few weeks. If not, Inner West Council assesses it as a DA, typically 13 to 17 weeks. Mid-spec duplex construction runs about $2,200 to $2,650 per m².
Written and reviewed by Oliver Alameri
Licensed builder, NSW Contractor Licence 487805C · Founder, Buildana
Fact-checked
Test one: is the lot in a heritage conservation area?
Ashfield has conservation areas in several pockets, and some individual heritage items. Complying development generally can't be used on a heritage item, and new dwellings on land inside a conservation area are generally excluded too.
So the first thing to check is your section 10.7 planning certificate. If the lot sits in a conservation area, a CDC duplex is off the table. The project becomes a development application at Inner West, and those typically run 13 to 17 weeks, longer once heritage gets involved.
That doesn't kill the duplex. Different path. Longer clock.
Half the CDC duplex enquiries I get in Ashfield end at the planning certificate. Check it first.
Tests two and three: lot size and frontage
Dual occupancy under the state's low-rise housing code needs a minimum lot area and a minimum frontage, usually around twelve metres measured at the building line. Many Ashfield blocks are 250 to 500 square metres on narrow terrace-era frontages, so a lot of them fall short.
The 2025 state low-rise housing reforms widened where dual occupancies are permitted in low-density zones across Greater Sydney, which helps. But permitted isn't the same as qualifying for complying development. The lot still has to meet the numbers, and the design has to meet every standard in the code.
Corner lots and the wider post-war blocks on some Ashfield streets are the most likely to pass.
- Not a heritage item and not in a conservation area
- Lot area meets the minimum for dual occupancy
- Frontage wide enough, typically around 12 metres
- Zone permits dual occupancy
- Design meets every code standard: height, setbacks, landscaping, parking
Does your Ashfield lot qualify?
Give me the street address. Planning certificate, lot size, frontage: I'll check all three and tell you plainly whether a CDC duplex works, needs a DA, or whether another project makes more sense.
0476 300 300If it qualifies: what a CDC duplex looks like
A CDC duplex has no room for negotiation. None. Height, setbacks, landscaped area, car parking and privacy are all fixed numbers, and on a tight Ashfield lot that usually pushes you toward a side-by-side pair with single garages or a carport each, bedrooms upstairs and living areas opening to small private yards.
A private certifier issues the approval once the documents show full compliance, typically within a few weeks. Neighbours are notified but can't object the way they can to a DA.
Building a mid-spec duplex costs roughly $2,200 to $2,650 a square metre (Rawlinsons, Sydney, unadjusted). Demolishing the existing cottage, often with asbestos, sits on top.
If it doesn't: other ways forward in Ashfield
A DA can still approve a duplex where the design has merit, even if it misses a numeric control. On a heritage lot, the answer is often a well-designed rear extension or a renovation instead.
Home renovations and extensions are the most common Ashfield projects we see: opening the back of a Federation cottage to the garden, adding a bathroom, or converting roof space on a steep-roofed house.
Your CDC duplex checklist for Ashfield
Run through these before paying for any duplex design.
- 01
Planning certificate: heritage item, conservation area, flood or other exclusions
- 02
Zone and whether dual occupancy is permitted on your lot
- 03
Exact lot area from the title or a survey
- 04
Frontage at the building line
- 05
Existing trees, easements and sewer that affect the layout
- 06
Whether you plan to sell one half, keep both or live in one
CDC duplex questions
Can I build a CDC duplex in a heritage conservation area?
Generally no. Complying development for new dwellings is generally excluded in conservation areas and on heritage items. Those projects go to council as a DA.
What frontage do I need for a CDC duplex?
The low-rise housing code sets a minimum frontage, commonly around 12 metres at the building line, along with a minimum lot area. We check your exact lot against the current rules.
How long does a CDC duplex approval take?
Once the documents show full compliance, a private certifier can typically issue the approval in a few weeks, much faster than a DA.
Can neighbours object to a CDC duplex?
Neighbours are notified, but complying development is assessed against fixed standards, so there's no merit-based objection process like a DA.
Sources and references
Costs are from the Rawlinsons handbook with the local cost index applied; rules and timeframes are checked against the sources below.
- Inner West Council
- Rawlinsons Australian Construction Handbook, Rawlhouse Publishing
- Environmental Planning and Assessment Act 1979 (NSW)
- State Environmental Planning Policy (Exempt and Complying Development Codes) 2008
- Asbestos, SafeWork NSW
- Search heritage databases, NSW Environment and Heritage
- NSW Planning Portal Spatial Viewer (zoning, FSR and hazard maps)
Know if it qualifies before you pay for plans.
A quick check of your Ashfield lot tells us whether a CDC duplex is realistic. Let's find out.