Building more medium-density homes could help ease the impacts of population growth across Australian cities, according to an expert.

Australia's population continues to grow at a rapid pace, spurring the need for solutions that can make cities more sustainable, said Mike Day, founder and director of RobertsDay.

Figures from the Australian Bureau of Statistics show just how fast the population is growing: In 1988, it predicted a population of 25 million by 2050. Day said Australia has already surpassed this level.

"Australia reached that estimate 30 years earlier. The ABS now projects a population of 30 million by 2030," Day said.

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At this rate, Day said Australia will need to house around 16.8 million more residents in the next 40 years.

"This is the equivalent of a new city the size of Canberra every year for the next 40 years, or a city the size of Darwin every 12 weeks," Day said.

Day said it is crucial for governments and urban planners to build sustainable cities that will not only maintain the standard of living and health of Australians but also provide local jobs, save water, create safe streets, and make housing attainable.

Need for medium-density housing

One of Day's suggestions is to build medium-density homes.

"This will bring residents multiple benefits. Townhouses and courtyard homes, with their turf-free outdoor spaces, will result in a significant reduction in water usage," he said.

And unlike apartment complexes, townhouses and terraces provide individual street frontages, which, Day believes, would allow residents to feel more connected to their neighbourhoods.

Furthermore, homeowners who design their townhouses like the terrace models seen in Sydney, Melbourne, Vancouver, Seattle, and Toronto, will be able to capitalise on their properties by building 40-square-metre granny flats above their garages.

Being able to design townhouse communities to be walking- and cycling-friendly is also important. Day said this can be done by making small streets at their rear that can provide access to garages.

"This minimises garages and driveways at the front of properties, enabling uninterrupted walking and cycling along tree-lined street frontages. This will improve safety and quality of life for pedestrians and cyclists," he said.

This shift to townhouses is actually happening in the prime residential market, according to a separate study by Knight Frank.

Michelle Ciesielski, head of residential research at Knight Frank, dubbed the trend "rightsizing", which appeals to a wide range of demographics including retirees and growing families.

However, supply remains a challenge, given the lack of approvals for medium-density housing options across the country.

New cities?

Locating new cities between Sydney and Melbourne will also help address concerns arising from the growing population.

"For instance, eight could be built along the Sydney-to-Melbourne high-speed rail service that is being considered by the government. Connecting the two cities provides an opportunity to promote the 'twin cities' of Melbourne and Sydney, considered by many as the world's most liveable and beautiful cities," he said.

It is crucial, however, to build urban cities from the ground up. Day says cities must be medium- to high-density at the outset and should be connected within by sustainable forms of transport and offer local jobs.

"A specific rapid mixed-use, walkable, urban city model is being advocated to federal and state governments by Consolidated Land and Rail Australia (CLARA), which is offering solutions to re-balance Australia's existing settlement and deliver new ways of planning and building liveable, sustainable, connected cities, transport and infrastructure," Day said.

Part of building new cities is ensuring the decentralisation of jobs. Day said Sydney and Melbourne would eventually benefit from additional outer-suburb mixed-use urban centres that will be placed in new cities.

"Any new cities that we build will require multiple ‘outer-suburb mixed-use urban centres with mixed-use retail, commercial and residential areas that are transit-based, compact and walkable. This will ensure short commute times and avoid putting pressure on transport systems and roads," he said.