How much does it cost to build a duplex? – Factors to Consider



How much does it cost to build a duplex? – Factors to Consider

Of late, duplexes have begun to experience a surge in popularity. With a duplex home, you essentially get two homes in one and only need a block of land. More importantly, a duplex in a well-chosen location can generate a high rental yield and capital growth. However, even when building a duplex, the costs can add up. So, how much does it cost to build a duplex? 

The answer to this question requires some discussion.

How much does it cost to build a duplex? 

When it comes to duplex development, there are a number of factors that need to be looked into as these can definitely impact the total cost of your project. These include the following:


In real estate, location affects property costs in many ways. If you already have existing land to accommodate your duplex, that’s well and good. However, if you have yet to purchase the land for the duplex to be constructed on, you need to be ready to shell out a substantial sum. Remember, land costs in popular or in-demand sections of the city tend to be high.

You need to ensure you have a great location that’s also guaranteed to get you the necessary approvals or permits to build a duplex from the local councils. Also, in selecting the best location for your dual occupancy building, you need to keep your investment mindset and ask the following questions:

  • Is the property located near the city or a commercial hub?
  • What amenities are found in your prospective neighbourhood?
  • Does it have good infrastructure?
  • Is population growth in the area steady?
  • Is there a high demand for rental property?

Work to avoid paying too much for your ideal property by looking for flat blocks, and look into the zoning of your plot, including future city rezoning plans affecting your property.

Surveys and reports

Planning for a residential building (or any building for that matter) entails using the necessary reports and surveys to help you decide on preliminary duplex designs, as well as to provide a basis for a specific list of expenses and building contracts.

Aside from land surveys, there are specific reports you need to submit along with the development application. These include the Australian Building Sustainability Association (ABSA) assessment report, landscape plans, statement of environmental effects, site analysis report, waste management report, BASIX report, shadow diagrams, storm water drainage design and Colour Schedule.

Site characteristics

You also need to work in the costs that can emanate from the physical attributes of the site. The site and survey results will reveal what costs may be incurred in the siting of the project on the lot.

Additional costs may include rock removal, retaining walls (brick or timber), site cut or fill, slab upgrade, and the compaction of existing fill. However, these factors are dependent on the condition of the soil and the fall of the land. Other costs you need to prepare for include the size and orientation of the lot, the block width, and all other requirements and documentation designed to satisfy the local council zoning and acquire the necessary permits.

To avoid wasting time, money and energy along the way, communicate with your local council right away. Familiarise yourself with the local building rules and regulations and required building-related documentation. Doing so will also prevent costly mistakes down the line.

Professional services

Duplex property investing may seem easy enough to plan or discuss; however, project execution is an altogether different deal. A duplex is not something you can DIY, even just partially. If you want a quality project outcome (as you surely will), you’ll need to utilise the expertise and services of different professionals from the very beginning through to completion.

An architect and a contractor (who will also hire subcontractors and other types of workers) usually take up the bulk of professional work and fees.

Some of the tasks handled by architects include:

  • Setting the scope of the duplex building project and helping set the preliminary budget
  • Drafting floor plans and helping create a schematic design
  • Accomplishing required documentation
  • Outlining preliminary plans
  • Reviewing plans and obtaining the necessary permits
  • Providing advice throughout the duration of the project

Contractors, on the other hand, take care of the following:

  • Depending on your agreement, the contractor will be in charge of hiring the required subcontractors and workers
  • Sharing ideas, comments and advice to help the developer meet their objectives
  • Ensuring all materials and services required are available
  • Assisting with obtaining work permits and in accessing utility installation

Materials and labour

The materials selected and used for your project will definitely add to the total cost of building your duplex. How much material is needed depends on the size of the project, and the cost will be determined by your preferences or requirements. On top of these, subcontractors, skilled workers and other manpower will have a major impact in determining the cost of construction.

Aside from the aforementioned items, other elements or features you include can impact your total building expenditure. These include:

  • House features, including termite protection, parking requirements, pollution barriers, etc.
  • Optional extras such as landscaping and fencing
  • Water and electrical systems
  • Safety requirements

If you need help with your duplex building project or need help with determining the cost, please reach out to us at Champion Homes. We’re experienced duplex builders you can depend on.

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