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Dual Occupancy Design on the Central Coast

Dual Occupancy homes are a great option allowing you to use your largest asset and potentially double it on the Central Coast.

Dual Occupancy Design on the Central Coast
Shea Cullen, Registered Architect at Good ArchitectShea CullenNSW Registered Architect 9748 · Updated 10 July 2026

A dual occupancy is two homes on one lot. It is one of the most effective ways to make a single block work harder, whether you live in one and rent the other, keep family close, or build both to sell.

On the Central Coast the lot size is the first gate. Under Central Coast LEP clause 4.1B you need at least 550m² for an attached dual occupancy, two homes sharing a wall, and 700m² for a detached one, two separate homes on the same lot, in the R1, R2 and R3 zones. There is no minimum lot width on the development application pathway, though the complying development pathway sets one of 15 metres, or 12 metres with rear lane access. Whether you can later subdivide into two separately sellable titles is a further question, and often the answer is no, so decide early whether you are chasing two titles or two incomes.

Use the buildable envelope tool on this page to see what your block can take, then work through the checklist below to plan the approval.

A survey tells you where your boundaries are, the level of everything, and where existing buildings and services are located. Council usually requires this with the DA. It also shows existing services so you do not plan to build over a sewer main, which can be expensive.
Contact council to discuss what you can do on your property. They will call you back.
A town planner has experience submitting projects to council and can tell you if your proposal is likely to be approved, or whether it has no chance. Avoiding nonviable projects can save you a lot of money, and dual occupancy feasibility covers the numbers to run before you engage anyone.
Get your architect to prepare drawings for a pre-DA meeting with council, then book the meeting through the council predevelopment meetings page.
Council will want to see this and the structural engineers need it to design footings at a later stage. It matters most on a slope, so check how steep your site is first.
Council will want a cost estimate, and you will want to make sure you can afford to build it. What it costs to build on the Central Coast gives you a sense check before the estimate lands.
Send the architectural set to a stormwater engineer who will design the stormwater system.
Your town planner writes this for submission with the DA. It outlines how the submission complies with or varies from the applicable planning laws, which on the Central Coast means the LEP and the DCP.
BASIX consultants make sure there is enough insulation, windows are thick enough and there is enough rainwater storage. BASIX is required by the NSW government for all additions over $50,000.
Council may request additional consultants depending on the project: an arborist report if removing trees, a bushfire report in a bushfire zone, an acoustic report near a busy road, or a social impact statement for larger proposals.
After approval, council provides conditions of consent. Common conditions include providing a concrete driveway and pedestrian path, which needs a Section 138 Roads Act approval, and state and local contributions of around $12,000 per dwelling, payable before the Construction Certificate is issued.
Send the updated architectural drawings to a structural engineer to design the structure.
Send the updated architectural drawings to a civil engineer to design the civil works.
Add a finer level of detail including wall types and concrete setout plans.
Your stormwater engineer updates their drawings for CC after the structural and other engineering drawings have been coordinated.
Work through the consent condition by condition. Common DA and CDC conditions covers the ones that catch people out.
Either council or a private certifier. It is often a good idea to engage them at the start of the process so they can give you a checklist, although they will only assess it at the end.
Pick everything from tiles to paint. This means the builder can price it accurately and you will not get stuck with a builder's margin. Anything left as an allowance is a provisional sum or prime cost item, and you pay the difference plus margin if it lands higher.
Get your architect to do detailed design drawings of everything that is not a typical detail, and all wet areas. Anything you want to be brilliant, get drawn up. Standard details can be left out. Wet areas are worth the extra detail, see what to check before waterproofing is covered.
Look carefully at what each builder is including and excluding in their quote, then compare the totals against what it costs to build on the Central Coast.
Check the licence, the insurances and the history before you sign. How to select a builder sets out the checks, red flags when choosing a builder covers the warning signs, and questions to ask before signing a building contract covers the contract itself.

You can see how this comes together on the Long Jetty duplex we designed as complying development, approved in a fraction of the usual DA timeframe without giving up design quality. See also the Wadalba duplex and The Outlook at Phegans Bay, two more dual occupancies we designed on the Central Coast. If you are still weighing the project up, start by checking what your site allows, and see before you build on the Central Coast for the whole journey from idea to keys.

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