Category: Duplex

Should your new home build be a duplex? Absolutely!

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Building a duplex (also known as a dual occupancy) is no longer the realm of property developers. In fact, everyday Sydneysiders are investigating the possibilities and the potential financial rewards.

What is a duplex?

A duplex is two dwellings located on the one block. In Sydney, they make great financial sense given the city’s high property values.

There’s no sacrificing style or amenities when building a duplex. They will still provide everything you want and need in a home and can be built:

  • Side-by-side
  • One in front of the other
  • One upstairs and one downstairs
  • Single or double story

While it’s common to build both homes the same size, it’s not a requirement. In fact the new trend is for a style of duplex called Manner Homes. They look like one large house but are 2 individual homes – often different sizes.

Why build a duplex?

The primary reason for building a duplex rather than an individual home is the financial advantages. It’s a way of maximising the value of your land by building one home to live in and another to rent or sell. Either way, you are using your land as an income source.

It also means family household expenses such as council rates are reduced because they are shared between the two properties.

In terms of costs, there’s not a lot of difference between building one or two homes on the same block. That’s why a duplex can be built as part of a knockdown rebuild project or a new home build.

Are there any differences between building a new home or a duplex?

When it comes to building a duplex, there are a few differences:

Difference 1:  You must have a Hydraulic (stormwater) Plan. It’s used to show how rainwater will be drained from your land and where it will go.

Difference 2:  You must also have a Landscape Plan which takes into consideration your local Council’s requirements as well as the Hydraulic Plan.

Difference 3:  The potential for subdivision. In some cases, your local Council may allow you to subdivide your property into either a Torrens Subdivision or a Strata Subdivision. This would allow you to sell each home as an individual property.

Like to know more?

Building a duplex is like building a home – you need great advice and someone to guide you through the process. At ZAC Homes, we’ve built over 300 duplexes so we’re able to advise you on whether a duplex is possible for your block. In fact, we can take care of everything for you including design, approvals, construction and demolition (if you are knocking down your existing home).

If you would like to explore the financial benefits and design possibilities of building a duplex, get in touch with ZAC Homes today.

The ZAC Duplex Difference

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ZAC Homes have been in business 20+ years and within this time we have seen all sorts of residential trends including the evolution of Duplexes (also called Dual Occupancies).

Dual Occupancies are two dwellings on the one block of land and can be attached or detached. Duplexes are a therefore a little more involved than doing a standard single dwelling, but when all you do is duplexes, you get pretty good at it!

Here at ZAC homes we want to make your Duplex process as stress free and simple as possible.


Firstly, you should ensure that Council permits a Dual Occupancy being built on your land. Most Councils will have a minimum lot size or width in which you must meet, in the first instance.

TIP: A current Council Section 10.7 certificate will have information on the permissibility of a Dual Occupancy, as well as information like bushfire or flooding, on the land. A quick call to Councils duty planner will let you know if there is a minimum lot or frontage requirement to build a dual occupancy along with any other special requirements e.g. subdivision. At ZAC we can help you with gathering this information if you need.


At Zac we understand that affordability associated with new developments is expensive. Being prepared for your preliminary plans and tender makes it easier and faster for us to get the ball rolling. Some points to consider are:

Budget: This can be a touchy subject, but the fact is duplexes cost more than a standard home, so budget is a big factor. Once you have an approximate budget, we can then work further with you to estimate your costs.

TIP: Having land that slopes towards the street is less expensive than one that slopes to the rear. Land that slopes to the rear requires a stormwater easement to be created or obtained.

Requirements: Do you need to demolish anything on the land (including removing any trees?) What size of house do you want? What kind of finishes would you like? Do you want to subdivide? Strata? Torrens? All these questions will need to be answered so we can quote packages to suit your needs.

TIP: ZAC homes speciality is duplexes. You can select these from our range (of 17+) or we can customise a duplex to fit not only unique blocks but also your unique requirements.


There are a few differences in the process that set duplexes apart from standard homes.

Hydraulic Plan: The most common misunderstood item is this. All duplex builds require a hydraulic (stormwater) plan designed by a qualified hydraulic engineer. The engineer will work to Councils requirements and other studies produced specifically for your stormwater catchment. The hydraulic plan shows how rainwater will be effectively drained from your land and where will it go. In most cases your hydraulics will also require On Site Detention (OSD) and often add a considerable amount to the overall price.

Landscape Plan: Working in conjunction with the hydraulic plan, Council will also require a Landscape Plan to be prepared by a qualified landscape architect/designer. As above, the landscape plan takes into account Councils requirements and the requirements of the hydraulic design.

The hydraulic design and Landscape plan (and price) cannot be fully worked out until your final plans are drawn and the house is confirmed.


In some cases, Council may have already advised you if no subdivision, Strata Subdivison or Torrens subdivision are permitted with the construction of your Dual Occupancy.  If subdivision is permitted this may be (in most cases) carried out at the same time as the application for the construction of the dual occupancy, or sometime after the dual occupancy is built. Some main differences are:

Torrens: This is the subdivision of one lot into two and there are no shared services.

Strata: If your land cannot meet the requirements for a Torrens subdivison you may be able to Strata title, similar to that of a town house or apartment building. This means that you will need to work with the resident of the other unit for joint concerns (maintaining driveway or roof, etc).

TIP: When you subdivide, you will need the help of a surveyor and / or conveyancer to change the details on the first title and to create an entirely new title that will represent the now separate second property. Once you’re the official owner to two legal residences, you can sell one or both at your leisure.

TIP: Zac covers everything from start to finish with your subdivision so if your undecided with another builder ask the question if they included these in their price?

  • Create additional power pole to both dwellings
  • Create sewer drainage to both dwellings
  • Additional NBN connections
  • Torrens / Strata subdivision plan
  • Final Torrens survey
  • Endeavour energy notice of arrangement
  • Endeavour energy Torrens application
  • Telstra arrangements letter
  • Stormwater provisions
  • Overhead wiring connections
  • New sewer junctions
  • Water service to dwelling
  • Strata title works to be carried out
  • Separate metering of services (electricity, sewer, water, gas)


We have been building duplexes for 20years + and specialise in knowing the best construction methods and giving the best advice for our clients. Key factors why our clients continue to build with us are:

  • Extensive range of 17+ duplexes
  • Broad range of façade options available
  • Customisation to suit your budget and requirements & Council
  • A Complete package price
  • Being upfront from your first meeting
  • Stress free process
  • Always updated throughout the build and council approvals

I hope this article helps answer any questions you may have with duplexes.