Fewer than a third of Australians own their home outright, but there are particular pockets of the country where a high proportion of Australians are sitting on million-dollar properties without a mortgage.

The country’s top mortgage-free suburb is Park Ridge in Brisbane’s Logan area, with a median price of $471,000, but it’s not the same trend being seen in Sydney and Melbourne.

In these two booming cities, the suburbs with the highest rate of fully-owned homes were predominantly million-dollar plus neighbourhoods, an analysis of census data for suburbs with more than 500 homes by Finder shows.

At the top of the list for Sydney was the lower north shore’s Longueville – with a median house price of $4.9 million on Domain Group data, with predominantly family homes, many with five bedrooms, on larger blocks of land.

Here, 57.5 per cent of home owners were living mortgage-free.

And in Melbourne, the top suburb was western suburbs’ Avondale Heights, closely followed by Bulleen and Wheelers Hill in the east. These are also relatively expensive locales dominated by detached houses.

In Canberra, one suburb had more than 50 per cent of homes owned outright – Isaacs with 50.9 per cent.

These areas are by far from average – the home ownership rate has been dropping across the country, and research shows more Australians will retire with mortgage debt than ever before.

Instead, they are likely representative of “long established suburbs with an older demographic who have paid off their homes,” Finder spokesperson Bessie Hassan said.

This tends to be home owners who bought in before real estate prices boomed.

“Certainly many of these suburbs are home to a lot of cashed up retirees. The data shows up to half of the population in some of these areas are aged over 55,” she said.

This compares to 27.5 pr cent of the Australia-wide population being aged 55 plus.

“But there are a suburbs – like Clontarf in Sydney or Macgregor in Brisbane – where the majority are young people,” she said.

In Clontarf, 52.5 per cent of homes are owned outright and 29.3 per cent of the population is aged 55 plus.

University of New South Wales City Futures Research Centre director Bill Randolph said it could be that many of these households “inherit wealth and therefore pay off their mortgages earlier than the rest of us”.

“So there may just be a lot of home owners who are wealthy enough not to have mortgages.”

Some of these areas have declined slightly from their home ownership rates in the 2011 census, but despite some locales doubling in value there have been only modest changes in the last five years.

This is likely due to home owners opting to stay put due to the high cost of stamp duty and the effect of selling on the pension, Real Estate Institute of NSW director John Cunningham said.

“This has caused a significant clog in the supply of homes to these already tight market places and despite the changes to superannuation laws in respect of the combined $600,000 non-concessional contribution in the recent budget it does not seem enough to get these properties on the market,” he said.

Though he conceded it could be “too early” to tell, with the changes only announced in May.

“The supply of existing homes to the market has a very big effect on housing affordability as low supply continues to push demand and as such we have not seen the usual significant dip following on from the boom years.”

Piers van Hamburg, director of McGrath Neutral Bay, Mosman, Northbridge and Chatswood, said many home owners were older empty-nesters who were staying put.

But he had noticed some in these tightly held areas opting to move to the coast, or to other states.

He said the homes in these suburbs tended to be larger properties, with entry-level higher than the $1.5 million mark.

There are only six properties on the market in Longueville at present – most with five-bedrooms.

This five-bedroom Avondale Heights home sold for $1,103,000 in August. Photo: Moonee Valley Real Estate

The trend was similar in Melbourne where it was “certainly the case” in the outer-eastern suburbs on the list, Mike Williams, a client liaison for buyer’s agency Wakelin Property Advisory, said.

“Many of the residents bought in the 1970s and 1980s. They were able to buy relatively affordable homes sitting on generous but not overly large land parcels,” Mr Williams said.

“Many might have assumed they would move away at some point in the subsequent years but, to their pleasant surprise, they found that the suburbs kept getting better, which meant they kept delivering the amenity they sought despite their evolving life requirements and tastes”.

Downsizing would be expensive, require moving away from friends and family and have “few obvious benefits”, he said.

“Indeed, when residents in the outer east do downsize, they often sub-divide, replacing the current house with two townhouses, one of which they live in.”

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