Adelaide is well known for its 19th-century stone buildings — but it is the city's divisive modernist and brutalist buildings that will be lauded at the world's largest architectural festival in London today.

Key points: Modernist and brutalist architecture was prominent between the 1950s and the 1970s

Modernist and brutalist architecture was prominent between the 1950s and the 1970s It was also a boom time for Adelaide so the city has a large number of the buildings

It was also a boom time for Adelaide so the city has a large number of the buildings Adelaide residents are more attached to the city's renown 19th-century architecture

Amid the London Festival of Architecture, at an event at Australia House, Stuart Symons will discuss Adelaide's mid-century architecture with fellow aficionados.

Mr Symons started his Modernist Adelaide Instagram page in 2012 and now runs tours in the CBD and suburbs explaining the architecture and history of some of Adelaide's more stylish buildings from the 1950s, 60s and 70s.

It was a time when Adelaide was growing quickly.

The surface of the Department of Education building on Flinders Street. ( Kevin O'Sullivan )

Mr Symons said people were growing more fond of the modernist and brutalist styles.

They celebrate the texture as well as the appearance of the concrete and steel they are made from.

"It's a style that's definitely having a sort of resurgence in popularity, at least online in terms of looking at these buildings from the 1960s and 1970s and kind of loving the fact that they're pretty dramatic and very, very bold," he said.

"You don't see many buildings like that at the moment.

"It's not necessarily to everyone's taste — some people would think they're concrete monstrosities — but I certainly love them and they've got a kind of heroicness that's pretty crazy that I really love."

Mr Symons leads a tour in Victoria Square near the former Reserve Bank building (centre). ( Supplied )

Two of Adelaide's most well-known modernist or international-style buildings are the former Reserve Bank building on the corner of Flinders Street and Victoria Square, and the MLC building on the other side of the square where it meets Franklin Street.

Both are on the SA Heritage Register.

Well-known brutalist buildings include the Department for Education's headquarters on Flinders Street, Wakefield House opposite St Francis Xavier's Cathedral and the ABC building in Collinswood.

The Department for Education's building has a rough-ridged concrete surface that has snared many cardigans.

"You can almost see a woodgrain in the concrete … It's deliberately roughed up," Mr Symons said.

The Maughan Church was demolished in 2016 to make way for a 20-storey building for Uniting Communities. ( Flickr: Gary Sauer-Thompson )

Difficulty in getting heritage listing

The modernist Union Hall at the University of Adelaide was demolished in 2010 and the Maughan Church on Franklin Street was pulled down in 2016 to make way for an office building.

Both were allowed to be demolished by the heritage minister while provisionally, but not permanently, placed on the State Heritage Register.

South Australian Heritage Council chairman Keith Conlon said neither demolition created the "broad outcry" that had previously accompanied the demolition of 19th-century buildings.

The Bureau of Meteorology building in Kent Town is set to be demolished. ( ABC News: Eugene Boisvert )

The council also refused heritage listing for the former Bureau of Meteorology building in Kent Town in July last year.

The 1977 building is set to be replaced with apartments.

Mr Conlon said for buildings to be listed based on their architectural merit, they had to be an "exceptional example" of their style and have "particularly strong artistic or creative qualities".

"People think that heritage has to got to be pretty," Mr Conlon said.

"It's actually not one of the criteria — an industrial building can be heritage if one of the criteria applies.

"So we've got to or I guess perhaps the architecture professionals and the heritage people have an educational job ahead of them.

"And then the Heritage Council has not an easy task to adjudge it in objective ways."

Mr Symons says the University of Adelaide's brutalist Napier building is vulnerable to demolition. ( Stuart Symons )

Older buildings closer to Adelaide's heart

Heritage consultant and former Adelaide city councillor Sandy Wilkinson said most Adelaide people were more interested in preserving the city's Victorian buildings than more modern ones.

He said 20th-century buildings were often built with lower quality materials and with less intricacy than older edifices because labour became much more expensive as Australia prospered.

SA Police's Wakefield Street office has "expressive concrete facades", according to conservation architect Kevin O'Sullivan. ( Kevin O'Sullivan )

"Buildings built when labour was cheap were higher quality," he said.

"They would cost a fortune to build now because they're so labour-intensive."

Some of them were also built from inferior materials during lean periods such as the Great Depression or World War II.

Mr Symons hopes talks like his today and his tours will build more understanding of the modernist and brutalist styles and their international context.

"Hopefully that leads to a bit of preservation," he said.

"It's about looking up and learning and appreciating and recognising that even things that are familiar that you might have walked past 100 times or gone to school there or worked there, you probably don't know much about it from a design point of view and the context of it.

'So that's probably just shining a light on a story that hasn't been told very much."