Thinking about building a duplex on your property? The first question is usually the simplest: can I actually build one here? The answer depends on a number of factors, including your property’s zoning, size, frontage, access, site conditions and the planning controls that apply to your area. The good news is that you don’t need to work it all out yourself.
At Homes by ZAC, we’ve been helping Sydney homeowners understand what’s possible on their land and turn that potential into well-designed duplex homes since 1993.
The simple answer: it depends on your property
There isn’t one rule that determines whether a property can accommodate a duplex. Two blocks that look very similar from the street can have quite different development potential because of their zoning, dimensions, planning controls or site conditions.
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Every site is different. Tell us a little about your property and our team can help you understand what may be possible.
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In this Article:
- What is a duplex?
- What makes a block suitable?
- NSW requirements
- Can I build on my existing home block?
- Can I subdivide a duplex?
- How Homes by ZAC can help
- Frequently asked questions
Important considerations
Two blocks that look very similar from the street can have quite different development potential because of their zoning, dimensions, planning controls or site conditions.
01 — Zoning
Does your property’s zoning allow dual occupancy development?
02 — Lot size
Does the property meet the applicable minimum lot size requirements?
03 — Frontage and access
Is there sufficient frontage and suitable vehicle access?
04 — Site conditions
Are there factors such as slope, drainage, easements, trees, bushfire or flooding that could affect the design?
05 — Building envelope
Can two homes, together with the required setbacks, private open space, parking and access, fit comfortably on the site?
06 — Planning pathway
Could the project potentially be approved through a complying development pathway, or would a development application be required?
That’s why the best place to start isn’t with a house design. It’s with your land.
What is a duplex?
In simple terms, a duplex is two homes on the same lot of land. The two dwellings can be attached, such as two homes joined by a common wall, or detached, depending on the site and the planning controls that apply. A well-designed duplex can provide an opportunity to create two quality homes where a traditional single dwelling might otherwise be built. It can also offer flexibility for different stages of life. You might live in one home and have family in the other. You could build with the intention of selling or renting one dwelling. Or you may simply want to make better use of a property with the right development potential.
The important question is whether a duplex is appropriate for your particular site and your goals.
What makes a block suitable for a duplex?
1. Zoning
The first thing to establish is whether dual occupancy is permissible on your property. NSW planning controls define different types of dual occupancy development, and the rules can vary between local government areas. Your property’s zoning, Local Environmental Plan and other applicable planning controls all need to be considered before you can determine what may be possible. Don’t assume that because your neighbour has built a duplex, you can too. Planning controls can change from one street, zone or council area to another.
2. Lot size
Lot size is an important consideration, but it’s not the only one. The applicable minimum lot size for a dual occupancy depends on the planning controls that apply to the property. In some circumstances, the relevant council’s Local Environmental Plan determines the minimum; other provisions may also apply depending on the development pathway. More land doesn’t automatically mean a better duplex site either. The shape and dimensions of the block matter just as much. A wide, relatively level block may provide considerably more design flexibility than a larger but narrow or heavily constrained property.
3. Frontage, access and parking
A duplex needs to work from the street as well as on the site. The width of your frontage, location of the driveway, vehicle access, parking requirements and relationship between the two dwellings all need to be considered as part of the design. This is one reason why simply dividing the block in half isn’t necessarily the answer. A successful duplex design needs to balance:
- Vehicle access
- Parking
- Private open space
- Building setbacks
- Privacy
- Natural light
- Landscaping
- The position and orientation of each dwelling
The aim is not simply to fit two houses onto a block. It’s to create two homes that work.
4. Site conditions
Your block may have characteristics that affect what can be built. These can include:
- Slope
- Easements
- Stormwater and drainage
- Existing trees
- Bushfire considerations
- Flooding
- Sewer and other services
- Existing structures
- Access constraints
- Heritage or environmental considerations
Some of these factors may have little impact. Others can significantly influence the design, cost or approval pathway. This is why a proper assessment of the site is so important before committing to a particular design.
What are the NSW requirements for building a duplex?
This is where things can become confusing. NSW has planning provisions that allow certain dual occupancies to be assessed through complying development, providing the proposal meets all of the relevant requirements. The Low Rise Housing Diversity Code includes standards for both attached and detached dual occupancies. But complying development isn’t available for every property or every duplex proposal. For example, the applicable planning controls can depend on the property’s zoning and Local Environmental Plan, while exclusions and site-specific constraints may affect whether the complying development pathway is available. Where a complying development pathway isn’t available, a Development Application may be required. The important point is that there is no single checklist that can tell you whether every property in NSW can accommodate a duplex. The property needs to be assessed against the controls that apply to it.
Can I build a duplex on my existing home block?
Potentially, yes. If you already own a house, that doesn’t necessarily mean you need to start again with a vacant block. A duplex project may involve removing the existing dwelling and developing the site, or in some circumstances considering other forms of dual occupancy development. The existing house, however, is only one part of the equation. Before deciding whether to knock down and rebuild, it’s worth understanding:
What is my property worth as it is?
What could I potentially build on it?
What would the finished development look like?
Would a duplex make financial and lifestyle sense for me?
That’s where a site-specific assessment becomes valuable.
Can I subdivide a duplex?
Building a duplex and subdividing it are two different considerations. Depending on the circumstances, it may be possible to create separate titles for the two dwellings, but subdivision is subject to its own requirements and approval pathway. So if your ultimate goal is to sell one dwelling, retain one, or own each dwelling separately, it’s important to consider subdivision at the beginning of the project rather than at the end. The design of the homes, access, services and proposed lot configuration can all influence the outcome.
What if I’m not sure whether my property qualifies?
This is probably the most common starting point. You may know that:
- your block is reasonably large
- duplexes have been built nearby
- your area is changing
- you’d like to build for two generations
- you’d like to downsize but retain another home
- or you’re simply wondering whether your property has more potential than a single home
But you don’t know whether your particular block will work. That’s exactly where we can help.
Ready to find out what’s possible on your property?
Tell us a little about your property and we’ll help you understand what may be possible.
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How Homes by ZAC can help
Building a duplex involves more than designing two homes. At Homes by ZAC, we can help you understand the opportunity from the beginning — from assessing your site and developing an appropriate design through to approvals and construction. Our experience with duplex and dual occupancy projects means we understand the practical considerations that need to come together to make a development work.
Site
We start by understanding your property, its characteristics and the planning considerations that may affect development.
Design
We then consider how two homes can work together on the site — balancing functionality, privacy, natural light, outdoor space, parking and street appeal.
Approvals
The appropriate planning and approval pathway needs to be considered based on the property and proposed development.
Construction
Once the plans and approvals are in place, our experienced construction team can bring the development to life.
From the first question about your block to the finished homes, we’ll help make the process simpler.
Is a duplex right for your property?
The best way to answer that isn’t by looking at a generic duplex plan. It’s by looking at your land. Your property’s location, zoning, dimensions, orientation and site conditions all influence what may be possible — and ultimately what type of homes can be created. If you’re considering a duplex, we’d be happy to help you take the first step.
Let’s explore what’s possible on your property.
Or speak with our team on 1300 350 793.
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