Before you embark on your grand plan to build a duplex, it is essential to start by doing a budget of available funds and the estimated costs.

A newly-built duplex is likely to cost between $650-850,000. 

Of course, it can be cheaper, or more expensive, depending on where you build and what you build. High quality materials, landscaping, fencing, or even a pool can all eat into your budget.

Then, of course, you need to have the land. If you’re buying a new piece of land to build your masterpiece, a land site in an inner-city area of Melbourne, for example, may start at $750,000 and go to $2 million.

Land in a regional area will be cheaper and there is some anecdotal evidence that, not only retirees, but those who are now telecommuting, are choosing to move further out of the city.

You’ll also need to figure in costs such as council charges and professional advice for planning approvals and financial and tax matters. 

A local real estate agent may be able to offer an opinion on likely rental return, if you intend to use half of the duplex as an investment property.

One cost-saving idea is to buy a house and land package. In that case, you will only pay stamp duty on the value of the land, not the house and land, as the home hasn't been built yet.

Choosing the right builder

Choosing the right builder for your duplex is also key to the success of your project.

While there are many companies offering building services, you should engage a builder who can demonstrate an understanding of how duplex developments differ from free-standing homes, says Robert Gullo, Operations Manager of duplex specialists Rawson Homes.

“Although quite similar in construction, there are a number of intricacies around the compliance with legislation for duplex developments,” he says.

On this subject, David Caruana, managing director of Arlington Homes, says: “Being able to interpret town planning regulations is important, as is having the skill set necessary to build your duplex.”

However, those aren’t the only factors you should look for in your project partner.

You don’t have to hire the biggest names in building to get great results.

But experience counts, so ask how long they have been in the industry, and whether their insurance is up to date, advises Caruana.

“You might also want to know whether they have a stable workforce, and what other services they can provide, for example, help with subdivision.”

Some building companies have specialist consultants, such as a town planner or engineer, to work through planning regulations with you and save you time and money, says says Robert Gullo, Operations Manager of duplex specialists Rawson Homes.

Others have consultants who can organise reports such as surveying or soil analysis.

Asking about all the services a builder supplies, or doesn’t supply, will help ensure a smoother building process from land acquisition to handover and quantify your costs.

Comment from our CEO

Downsizing.com.au CEO Amanda Graham said that, as State Governments across Australia continued to encourage duplexes as a new housing option, more builders were preparing ready-made off-the-shelf duplex designs.

“It’s well worth checking out the websites of builders to see what sort of designs they are offering, including their architectural style and pricing,” Ms Graham said.

Find out more

We've published a series of stories to help downsizers building duplexes.

Click on the links below to find out about:

Helen Hawkes is a business and lifestyle journalist who has written for clients including CPA Australia, Westpac, Colonial First State, The Australian Financial Review, QSuper and the Australian Institute of Superannuation Trustees. She is also the owner of interior styling and homewares business The Little Green Room. Helen has bought and sold five houses and is currently planning a comfortable retirement.