All five state mainland capitals feature in most expensive top 20 places to buy: Demographia

Sydney rates as the second-most expensive city for house prices globally, priced out only by Hong Kong for the second year running, according to international research group, Demographia.

Australia has five of the 29 cities rated in the group’s annual Housing Affordability Survey as “severely unaffordable.”

The median price of a house in Sydney was 12.2 times the city’s annual median household ­income.

In Hong Kong it was 18.1 times. Vancouver ranked the third-most unaffordable city at 11.8 times.

Auckland ranked fourth.

Melbourne have slipped out of the top five this year, ranked sixth in 2017 and more expensive than Los Angeles and London.

Adelaide, Brisbane and Perth all featured in the top 20.

Some 11 of the most affordable housing markets were in the US, according to Demographia, which looked at 406 cities of which 95 were major metropolitan centres with a population of more than 1 million.

Demographia listed Australia's major problem as urban containment policies.

Commonly called 'greenfields', urban containment plans aim to reduce the growth of the urban sprawl by encouraging greater density in existing housing areas.

New NSW Premier Gladys Berejiklian announced before the news that she would address the states housing affordability crisis.

To read the full Demographia report click here.