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Promoted by loans.com.au

Building a duplex, which is two separate homes with a dividing wall on one block of land, is one of the easiest ways to add instant equity. But how much does it cost, and can you do it without breaking the bank?

We all love a good deal, which is why duplexes are a popular investment option. Duplexes are high-yielding, high-growth investments that require a higher upfront financial commitment than if you were building a single freestanding home. However, it’s usually cheaper to build a duplex than it is to build two freestanding homes because both dwellings are on the same block of land.

Duplexes have the potential for significant profits which is very lucrative for investors, but there are hidden costs so determining whether a duplex is a good investment requires some number crunching.

Cost of building a duplex in Australia

There are many factors that determine the final price of constructing a duplex, such as the location, materials, architects, and land costs.

According to Oneflare, the average cost to build a duplex in Australia (excluding land costs) ranges between $550,000 and $1.3 million.

Costs in Australia


Average Reported Costs


$600,000 – $1.2 million


$650,000 – $1 million


$550,000 – $1.1 million

Source: Oneflare

According to Masterton Homes, the total cost of building a two-story duplex would not be under $650,000.


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Factors impacting the cost of building a duplex


One of the first steps when planning a duplex construction is undertaking the required surveys and reports that will determine the condition of the block of land. The results found from these surveys/reports will then help to determine the costs associated with factors relating to the siting of the home on the block of land, such as rock removal, retaining walls, slab upgrade, etc.

The size and orientation of the block of land, the width of the block, local council zoning, and planning permit conditions will also impact these costs.

The location of the block of land will also impact the building cost. Demand for land in the area will impact the value of the land and the price to build a duplex.

Contractors and architects

The types of contractors and architects and their skill levels can also impact the cost of the build. Architects take care of the outlining of the dimensions of the duplex, assist with the budget, design layouts and floorplans, get the required permits, and more. Contractors hire the required workers and subcontractors, brainstorm ideas and make inputs to the developer, assist in acquiring permits, and ensure materials and services are available.


The type and quantity of materials used can have a significant impact on the cost of building a duplex. The quantity of materials is determined by the dimensions of the project. In addition, the availability of materials can also have an impact on the cost. The residential construction industry is currently impacted by an Australia-wide shortage of building materials and skilled trades, which is blowing out construction costs.


The location of the site where the duplex is built will also have an impact on the cost. If you’re building in an area where there is strong demand and a scarce supply of vacant blocks of land, the costs will be higher. If you already own the land where you want to build the duplex, it’s quite an advantage.


If you’re knocking down an existing dwelling to rebuild a duplex, you will also have to fork out for demolition costs. Demolition costs can range between $10,000 and $30,000 according to Oneflare. Depending on the quality of the existing dwelling, you may be able to recycle some of the materials.

Take out a construction loan

If you’ve decided to build a duplex as an investment property, loans.com.au can take the stress out of financing your building with our low rates and easy online application.

Our Investor Construction loan has a rate of 7.29% p.a. (7.23% p.a. comparison rate*) and is a great option if you’ve bought land and are ready to build.

How to apply for a construction loan 

You'll need all the usual items required for any home loan application, including:

  • Identification 
  • Employment information 
  • Payslips and pay summaries
  • Lists of assets and liabilities 
  • A savings history 

In addition to all of this, you'll need to present professional plans for the property, including an expected valuation. Having a bigger deposit can help too. 

If you’re interested in building a new home, chat with one of our lending specialists today to get pre-approved for a construction loan.

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