Why there's no fixed quote
Duplex approval cost and time depend on the approval pathway, the complexity of your site, the consultants required and how the council responds. A clean CDC on a regular lot is a very different exercise to a DA on a flood-affected, heritage-adjacent block. We give a tailored scope after a feasibility check, never a made-up flat rate.
Timeline: the honest ranges
- CDC: as fast as ~20 days for determination once documentation is complete, but design and documentation take time before that clock starts.
- DA: typically several months, varying widely by council, submission quality and whether an RFI is issued.
- Design and documentation before lodgement: allow additional weeks for feasibility, concept, consultant coordination and finalising drawings.
What moves the cost
- Pathway: CDC vs DA (a DA generally needs more reports and coordination).
- Consultants your site triggers: surveyor, BASIX/NatHERS, stormwater, arborist, bushfire, heritage, geotechnical.
- Site difficulty: slope, flood, bushfire, heritage and battle-axe access all add scope.
- Council fees and any required variations (e.g. a Clause 4.6 request).
How to keep it efficient
The cheapest project is the one designed for the right pathway the first time. A proper feasibility up front avoids the expensive mistake of drawing plans that can't be approved, the single biggest cost blowout we see.
Frequently asked questions
It varies by council, but a DA typically runs several months, and longer if an RFI is issued. A CDC on an eligible site can be determined in as little as around 20 days once documents are complete.
Because an honest price depends on your site and pathway. We scope it properly after a quick feasibility check rather than quoting a number that later changes.
Authoritative sources: NSW Planning Portal.