With their broken, boarded-up windows and graffiti tags, Adelaide's vacant heritage buildings are a world away from the charming apartments that line the grand boulevards of Paris.

Despite their dilapidated appearance, ABC reader Margaret-Ann Copeland has harboured a dream of converting a North Terrace building into a Parisian-style apartment since she was a teenager.

"Years ago I worked over on an old building on Victoria Square … and when I got a job in there, I felt like I had been to Paris. It would have made such a nice apartment, I felt like I was in a French movie," she said.

"I just look at all the buildings on North Terrace and they're so beautiful, and it's such a shame that on the southern side there's all these vacant buildings.

"I just have no idea who owns them and why such beautiful buildings are empty."

Now a teacher in her 50s, Margaret-Ann asked Curious Adelaide: Who owns the heritage buildings on the city's equivalent of the Champs-Élysées and why have they been left boarded up for decades?

Who owns the buildings?

Over the years, there have been promises and delays to revitalising the southern side of North Terrace, which is one of the city's major thoroughfares and is lined by long-neglected heritage buildings.

One of the most prominent buildings, the Gawler Chambers, has been owned by the Roches, a wealthy Adelaide establishment family, since 1945.

Comparison of the former Tuxedo Cat venue with its proposed redevelopment. ( ABC News: Rebecca Puddy / Commercial & General )

The family business, Adelaide Development Company (ADC), has plans to transform the site into a multi-level commercial office tower behind the 1914 heritage facade but they have been on hold for the past seven years.

ADC chief executive Ian Marker said the company had development approval but wanted to lock in an anchor tenant in the "very tight market" before proceeding with the build.

Down the road, plans to redevelop 200 North Terrace — including the former home of Fringe venue Tuxedo Cat — are similarly proceeding at a slow pace.

Consent was provided in November for owner Le Cordon Bleu to continue planning their 19-level combined retail and commercial office tower.

Next door, at 203 North Terrace, windfarm developer CATCON has put on hold plans for a "groundbreaking" 18-storey residential living complex behind the facade of the building once owned by G&R Wills.

One of the heritage buildings had a sculpture aimed at neighbouring David Jones. ( Supplied: annystudio.com )

A lands title search shows a smaller gothic building at 207 North Terrace is owned privately by a company run by former lawyer Lorraine Thomson.

The building previously had a unique hand sculpture erected on its facade, cheekily directing a raised middle finger in the direction of the neighbouring David Jones building.

Why are they empty?

North Terrace is currently a partial building site because of work on a tramline extension, which is currently being installed to encourage revitalisation of the city's East End precinct.

But Adelaide's Lord Mayor Martin Haese, who describes the street as Adelaide's Champs-Élysées, said special planning considerations are needed to entice investment.

"If a building ultimately in the long term is not being used, you've got to ask yourself if it's serving any community good," he said.

"How long can they stay empty in the hands of one owner?"

North Terrace has been described as the Champs-Élysées of Adelaide. ( Supplied: Flickr/Mark Kobayashi-Hillary )

Gillian Armstrong, who is completing a PhD at the University of Adelaide on the adaptive reuse of old buildings, wants a more proactive approach to encourage redevelopment.

"Waiting for the right development hasn't worked," she said. "Everything comes down to the economics and you've got to find the use that will fit the market and building.

"I think that if you're not prepared to develop them, you should sell them to another owner."

According to Property Council executive director Daniel Gannon, explaining why the buildings have languished is complicated, but gets down to taxes, planning and population.

"Adelaide is facing myriad economic challenges right now," he said.

"Without sustainable population growth, the property sector and our state are at risk of losing investors and gaining more octogenarians."

He also pointed to concerns about safety which were highlighted in the wake of London's Grenfell Tower disaster.

"With issues around the Building Code of Australia, fire safety and disability access, there is a real challenge in attracting the kind of investment to bring these old buildings up to scratch," he said.

From bustling boulevard to divided street

The building restrictions have created a divided North Terrace, with the northern side of the road home to South Australian institutions including universities, the Royal Adelaide Hospital, SAHMRI and Parliament.

"There is a real possibility that we will have a city of two halves in the future — where one part of the city is modern and new and the other is old and underutilised," Mr Gannon said.

Keith Conlon says North Terrace needs special attention from the Government. ( ABC News: Rebecca Puddy )

Local media personality Keith Conlon, whose interest in state history has seen him dubbed Mr South Australia, runs tours of Adelaide, including along North Terrace and its heritage buildings.

The incoming chair of the South Australian Heritage Council said that unlike the northern side, which has always been home to cultural institutions, the southern side was once home to private residences and a "medical alley".

"Before the towers were built right up to the 1950s, private residences almost all got taken over by professionals, doctors and dentists," Mr Conlon said.

"It was a main thoroughfare in the horse-and-cart era, and then in 1909 the trams came and the automobile followed after that."

He said the Gawler Chambers on the corner of North Terrace and Gawler Place had real historic interest to the state, having been built by the South Australian Company, a London-formed colonial investment arm.

North Terrace was once a boulevard of medical practices and private homes. ( State Library of SA: Henry Krischock )

Why don't other states have this problem too?

Mr Gannon said one of former Victorian Premier Jeff Kennett's greatest legacies was creating a resident population in Melbourne through Postcode 3000, a strategy redeveloping ageing buildings into multilevel residential complexes.

But this could not necessarily translate to Adelaide, where small-to-medium-sized family owned businesses owned properties rather than institutional investors.

"This means that innovative landlords can have a big impact and influence on certain precincts, like the Peel and Leigh Street laneways, or the vibrant East End," he said.

"But it also means that some of our office stock needs investment."