Home » Blog » How Much Does It Cost To Build A Duplex In Sydney?

Many Australians today choose to live in duplexes, whether building a duplex themselves or getting contractors to build them, as the multi-storey, side-by-side design increases in popularity. 

While the cost to build a duplex can vary, families that choose to buy a pre-built duplex could see interest rates between 6 and 7%, with the current variable home rate at 6.61% p.a. and the Big Four banks offering an even higher rate of 7.20% p.a., with the Royal Bank of Australia holding the cash rate at 4.10%. With a steady reduction in inflation, construction costs will slowly be reduced in the coming months. 

Not only is this good news for homeowners, but it also means that property investors can look forward positively and make moves to acquire new additions to their portfolios, such as highly profitable duplex development. Duplexes are particularly profitable to rent.

One of the most challenging aspects of building duplexes is understanding how a duplex cost can vary within the same city. Sydney is New South Wales’ capital, covers more than 4,770 square miles, and is home to more than 5.5 million people. 

As such, there are a multitude of factors that contribute to a duplex build cost, including where the property is built. Let’s explore the cost variations across Sydney to help you decide where best to put your next duplex project.

Sydney Central Business District

If you’ve always been a city-slicker and have been desiring a move to the centre of it all, then building a duplex in the Sydney CBD will mean building up and not out. As real estate space is at a premium, expect to pay a high price for your block of land before you’ve even laid a foundation. This pricing estimate of roughly $2,800 per square metre will mean that you’ll have to take advantage of a multi-level duplex, depending on your build’s purpose. 

The idea of building duplexes in the Central Business District received a huge boost earlier this year when the Government of New South Wales approved an amendment to existing housing legislation that brought duplexes under the fold of suitable development plots. 

This rule change meant that duplexes could receive council approval in as little as 20 days, allowing construction to occur on a tighter timeframe. The objective of the change was to encourage property developers and homeowners alike to build medium-density housing on smaller plots of land to ease the housing crisis gripping the country. 

Sydney Inner West 

The Sydney Inner West is one of the fastest-growing neighbourhoods on Sydney’s west side, located 15 minutes by car from the Central Business District. This bustling part of Sydney contains three malls, a home improvement store, and an IKEA store and is home to Sydney’s Olympic Park and Aquatic Centre.

Sydney’s Inner West has several vacant land lots for sale, upon which one could build a duplex. Being a mere 15 minutes from the CBD makes Sydney’s Inner West perfect for the busy commuting family. 

It is a great option for real estate investors looking to expand their portfolio without getting too close to the CBD. The average price to build a duplex unit in the Inner West is between $900,000 and $1,600,000

Sydney Eastern Suburbs 

Sydney’s Eastern Suburbs are the eastern metropolitan region of Sydney, bordered by the CBD to the west and the gorgeous South Pacific Ocean to the east, and it’s also the home of the world-famous Bondi Beach. 

Sydney’s Eastern Suburbs offer a hot climate and real estate market. With an average price of between $1,800,000 and $4,000,000, you can score a fantastic deal on a duplex within short driving distance of Bondi Beach and myriad other beaches dotted along the Pacific Coast and Malabar National Park, a beautiful forested paradise on the ocean.

Sydney Northern Beaches 

Sydney’s North Shore is a gorgeous, sprawling area mostly home to Garigal National Park and Ku-ring-gai Chase National Park, two spectacular parks 30 minutes from the Central Business District. Building a duplex in Sydney’s North Shore means being on the cusp of one of Australia’s most beautiful natural wilderness areas, filled with hiking trails, mountains, beaches and much of the country’s infamous wildlife. 

With the average price to build a duplex in Sydney’s north fetching an eye-watering $1,550,000, living this close to the paradisical national parks and only half an hour from the hustle and bustle of the CBD, it’s the ideal duplex build location for those looking to be closer to nature but within driving distance of civilisation.

Greater Western Sydney

The average price of a duplex in Greater Western Sydney is between $900,000 and $1,200,000.

With a sprawling metropolis to the east and the stunning Blue Mountains National Park to the west, Greater Western Sydney (encompassing Western Sydney) is an eclectic blend of the modern metropolitan and the natural world. 

Home to wildlife parks, shopping malls, leisure centres and more, the many subdivisions of Greater Western Sydney make for fantastic places to build a duplex to accommodate the thriving student population at Western Sydney University or the families looking for that blend of city life and the wonderments of the nature on their doorstep. 

Southern Sydney 

Southern Sydney is home to the spectacular Botany Bay and St. George’s River that flows into it. Many of its suburbs are separated from one another by the water, which can be enjoyed year-round by boating enthusiasts of all types.  

By investing in land in Southern Sydney, you can attract retirees from the CBD and the budding professional who enjoys the quiet serenity of an hour’s drive from the downtown core. Despite being far from the CBD, Southern Sydney’s property prices are pretty high, sometimes stretching to over $1.5 million

According to community demographic research, you can also expect to be surrounded by a multicultural hub, as many of Southern Sydney’s residents speak a first language other than English. As a property investor, the Southern Sydney region is a fantastic opportunity to latch onto a growing property market that’s becoming popular with foreign investment from all corners of the globe.

Sydney Inner City 

The Inner City of Sydney is also known as the City of Sydney and is home to over thirty suburban regions and encompasses a compact of only 25 square kilometres. The compact nature of the Inner City region means that property developers who want to build a duplex must build up — and not out — to accommodate the available land.

However, as one can quite comfortably build up to two storeys high in NSW, buying up multiple smaller blocks of land and putting two-storey duplexes on them is a very attractive option looking to stay closer to downtown Sydney.

Southwestern Sydney 

For those seeking rental opportunities for multiple families, the working-class area of Southwestern Sydney provides ample opportunity. As this area is located on the Cumberland Plain, you’ll be bordered by the gorgeous Royal National Park and Fieres Crossing Reserve.

Home to the small neighbourhoods of Woronora, Kirawee, Bangor, Lucas Heights and others, this area is perfect for those seeking to build multiple units at affordable prices for the location, coming in at under a million in many instances.

Sydney Hills District 

The Sydney Hills District is a beautiful region of Sydney that lies north of the city centre and is high in white-collar workers and high home prices, backdropped by the fantastic sprawl of Marramarra National Park.

Despite being a white-collar work area, the housing prices in the Sydney Hills aren’t outrageous, A duplex build in the Sydney Hills District can cost $900,000 and above. 

Duplex costs in Sydney 

Sydney is an incredibly attractive city for property developers, from the thriving CBD to the much quieter, serene foothills. Building a duplex in the city is well worth the alarming investment of an average cost of $2,400 per square metre and an average size of at least 500 square metres, putting the average cost at $1,000,000. However, these construction costs will vary greatly depending on various factors.

1. Materials and labour 

When budgeting for a duplex build, you must first consider what type of materials your duplex will be built from. While the cheapest way to build a home in Australia is either a flat-pack home or one made with a steel frame and a corrugated steel exterior, duplex designs tend to involve more substantial materials and incur a higher cost. 

Regarding basic building materials, cinderblocks and brick are primarily used in the home’s foundation or a concrete pad. Native timbers like Cypress Pine, Blackbutt and Jarrah are among the most commonly used in home construction for flooring. Native pines, including duplexes, are used as framing timbers in most home construction. 

Additionally, Australian paper-faced plasterboard is commonly used internally as cladding for the framing. However, when building a duplex, it is essential to consider spending more money on soundproofing and insulation, as you (or your tenants) will be living next door to or on top of other people. 

2. Additional expenses 

Before you’ve even begun your project, once you’ve chosen your land, you must ensure that surveyors have tested the soil and that it meets the soil classification guidelines and passes testing. Other site costs include if your duplex is constructed on a slope and needs a retaining wall. This can be particularly common in the Sydney Hills region. 

Add special features to your custom home, such as solar panels, passive solar heating options, or other eco-friendly design elements. Then, you’ll need to adhere to NSW environmental regulations and receive a BASIX Certificate.

3. Professionals 

On top of the materials and labour costs, other remunerations must be made for pest control once the custom home is complete. You must also ensure that a structural engineer has inspected the build and an inspector has signed off on all completed plumbing.

Other building costs include hiring architects, roofers, bricklayers (if constructing your duplex with brick), plumbers, electricians and other professionals. Your desired custom home contractor may also hire these professionals for you.

While it is possible to DIY some home construction to reduce construction costs, it isn’t allowed when dealing with electrics, water supply and distribution, or anything related to the structural integrity of your building.

The average cost for an electrician in Sydney is $80 to $130 an hour. Meanwhile, the average cost of a plumber in Sydney is $100 an hour. While a good electrician or plumber can get things done relatively quickly to keep the project on track, expect to pay a premium for additional contracted services.

4. Location 

One of the prime drivers of the cost of building a duplex in Sydney is precisely where you’ll be building. With a population of over 5,000,000, the city is one of the country’s most populous. Although it covers a vast area, different areas of Sydney have different zoning laws that can prohibit property development of certain types of property. 

In June of this year, Sydney became the most expensive city to build a home in, replacing Brisbane on the Gold Coast. Other locale-based considerations include the population density of where you’re building, as a more populated area will increase the cost of building a duplex due to supply and demand. 

Additionally, land prices are higher in higher-population areas. Living closer to Sydney CBD’s amenities will incur a higher build cost. Before buying land and building a duplex, check Sydney’s zoning laws with the New South Wales Department of Planning. The zoning laws of the city or those within your chosen location may not permit your building design, so you may have to make some adjustments to stay within the rules. 

5. Land costs 

Aside from the overall cost of buying land in Sydney, you must also consider what changes you may need to make to the land before it can be built. For example, putting in a retaining wall built on a hill or ensuring adequate drainage and flattening the land by removing rocks and boulders to give you an even surface to start your build on.

6. Size and demolition 

If you are performing a knockdown rebuild, you’ll need to assess the cost of demolition and safe disposal of your construction project waste before you put your new building on top of the old foundation (which will need to be inspected first).

A final consideration: if you have the land to build a side-by-side duplex rather than a top-and-bottom type of duplex, your building costs will be reduced slightly, as building side-by-side is less complicated (structurally) than building a two-storey building.  

Other hidden costs 

These costs are sometimes known as ‘hidden costs,’ I.e., costs that aren’t readily apparent but those that you’ll be hit with later at the end of the project. These hidden costs can include: 

1. Landscaping

While it’s good to put in a driveway as part of your initial estimate from a concrete contractor, other landscaping quotes include lawn care, garden edging, tree and flower bed planting, and more. These landscaping costs aren’t always included in the original quote from your contractor. You may need to go to a professional landscaping company to obtain quotes separately from your house-build cost calculations.

2. Taxes

There are two certainties in life, as they say. Taxes are one of them. When calculating your duplex cost, you must include taxes in your budget. Taxes on everything from your contractor’s quote to more obscure taxes like land taxes, deed transfer payments and stamp duty if you’re purchasing land from another owner.

3. Industry cost fluctuations 

The cost of living is one of the worst crises to hit Australia. A supply-and-demand crisis on everything from fruit and vegetables to necessary construction materials like steel and wood has exacerbated this. If you choose imported materials for your duplex construction, prepare for material shortages and increase production costs. 

The benefits of building a duplex in Sydney 

Now that you’re aware of many of the associated costs of living in the capital city of New South Wales, let’s talk about some of the many benefits of building a duplex in Sydney. 

1. Rental income 

One of the main benefits of building a duplex in Sydney is that it will generate a rental income. Renting out both sides of a duplex is a fantastic way to generate thousands of dollars of income. 

With the city and the country more broadly in a housing crisis, the phrase “build it, and they will come” has perhaps never been more true. The housing market is crying out for rental properties, and building a duplex allows one much more rental flexibility than building a single-storey home.

2. Cost-efficiency 

One of the main appeals to building a duplex is that they are more cost-efficient to produce than single freestanding dwellings. This is because the duplexes can mirror each other’s design, allowing them to be built faster and take less time to plumb and electrify, regardless of whether they are top-and-bottom or side-by-side duplexes. 

Despite their significant upfront investment, once you rent out both units, your rental income may be higher than that of a single-storey home.

3. Flexible living arrangements 

Duplexes offer a level of flexibility that other housing options often lack. One of the beautiful things about building duplexes is that they provide flexibility for living arrangements. 

Whether you’re adding a second-story granny flat for a family member’s residence or constructing a side-by-side duplex as a separate home, you may be considering renting out one side to students or a family to help with your mortgage expenses. 

4. Family-friendly 

When it comes to building duplexes in Sydney to rent to family units – even having two families living on either side of a side-by-side duplex, Sydney is incredibly family-friendly. There are over a million hectares of nature preserves and parks, kilometres of hiking, walking and cycling trails, dozens of schools to choose from and a relatively low crime rate. 

Building a duplex in Sydney will answer the call of many families looking to move to or rent in a larger city from elsewhere in the country or from abroad.

5. Desirable location 

As the capital of New South Wales, Sydney has been a desirable location for property investors for many decades and is notably stronger this year following a bounce-back. As inflation comes down and the cost of living decreases, many may choose to look again at living in a major Australian city. 

Low-maintenance properties 

Unlike many freestanding homes, duplexes are low-maintenance properties despite being two properties on a single plot of land. It also means less exterior maintenance with things like lawn care, as you would mow the whole property once and take care of the lawn for both tenants, as the block of land is smaller than your typical home. 

In addition, renting out both sides of a duplex means an additional security benefit to tenants, which means that you can reduce the cost of keeping a security camera on at all times or paying property managers to check on the property as the tenants become each other’s ‘security’ guards, without being sandwiched together like sardines as in many apartment buildings.

Future development of land 

If you buy a large parcel of land, you have the opportunity to build two-storey duplexes that you can then add onto the same parcel of land; owning two two-storey duplexes enables you to quadruple your rental income while maintaining a small plot of land. 

The possibilities are endless. Multi-storey duplexes take up less space, and you can buy multiple blocks of land and develop on them slowly or spruce up the backyard with landscaping, an outdoor garden shed, or add a swimming pool or granny flat.

Looking to build a duplex?

Duplexes are a fantastic option for many already on the property or those looking to answer the call of many Australians looking for rentals. With their design versatility, multi-storey options, and small footprint, they can be built relatively inexpensively for their potential rental yield and sales price further down the road. 

For those looking for your next investment opportunity or family home option, consider building a duplex with Worthington Homes, a veteran custom home designer and builder with decades of experience serving Australians. 

From our award-winning kitchen and bathroom designs to our fully-built custom homes. Whether you’re building a granny flat addition to your existing home or want your duplex to be completely customised and built to your exact specifications, our custom home builders are home design experts. 

Contact Worthington Homes today to get you on your way to owning your dream duplex or your next property investment.



News and inspiration from our blog

Are Duplexes a Good Investment? Here’s Everything You Need to Know

Duplexes are becoming more popular as a real estate investment opportunity among experienced real estate investors and as a reliable income generator for those looking to enter the real estate…

How Long Does it Take to Build a Duplex?

Duplexes are fantastic options for real estate investors looking for long-term, high-return rental opportunities, or for family units looking for their next family home on one side, with a rental…

The Knockdown Rebuild Process: Your Ultimate Guide


Whether you’re just buying your first home, or have been in the property game for a while, engaging in a knockdown-rebuild of an old home to put a new one…