Sydney's traditional stand-alone homes will be outnumbered by apartments, townhouses and terrace houses within seven years, according to new research.
Over the past 25 years, the share of detached homes in the city has fallen from 68 per cent to 55 per cent and, if the trend continues, detached houses will be in the minority by 2024, a report by demography company McCrindle predicts.
The 2017 Sydney Lifestyle Study, commissioned by Urban Taskforce Australia, which represents property developers, drew on 2016 census data and a survey of 1500 households to analyse the lifestyles and attitudes of Sydneysiders who live in high-density accommodation.
While Sydney's apartments are most likely to be occupied by singles (34 per cent) or couples (27 per cent), the report highlights rapid growth in couples with children living in apartments. These households - dubbed "vertical families" - jumped from 65,000 families in 2011 to more than 87,000 in 2016, an increase of 34 per cent.
One in five apartments in Sydney is now occupied by couples with children.
The top five suburbs for these vertical families are Parramatta, Bankstown, Westmead, Liverpool and Campsie.
There has also been strong growth in the share of apartments occupied by single-parent families; they now account for 8 per cent of those living in high-density accommodation. The number of single parent families in apartments has grown by 14 per cent since 2011.
Report author Mark McCrindle said the prevalence of families with children living in apartments represented a major demographic shift for Sydney.
"Couples with children is one of the fastest growing segments in the apartment category," he said.
Last year's census showed Sydney now has more than 100 suburbs where half the population or more lives in an apartment.
The shift to higher-density living is being driven by factors including proximity to employment, changing lifestyle preferences and housing affordability.
Sydney has a bigger proportion of apartments, townhouses and terrace houses than other Australian capitals but, overall, the share of high-density accommodation in Australia is low compared with many other industrialised countries.
Those living in Sydney apartments are relatively young and well educated. McCrindle's study finds 54 per cent have a bachelor degree level of education or higher compared with 40 per cent of those living in detached housing.
Apartment dwellers are also much more likely to be tenants: 63 per cent of Sydney's apartments are rented compared with just 18 per cent of detached homes.
Those living in apartments are very mobile and 55 per cent have lived in their current home for less than five years. They are also much more likely to be born overseas than those living in detached homes.
The report forecasts the share of detached houses to fall to just 25 per cent of Sydney's housing stock by mid-century.
"Towards the end of the 2050s, apartments will become the most dominant housing type of any other accommodation in Sydney," it said.
Chris Johnson, chief executive of Urban Taskforce, said the research highlighted the need for services catering for families that opted for high-density living.
"There are crucial messages to the development industry about the design of family friendly apartments with amenities such as child care nearby," he said.
The research also finds Sydney's apartment dwellers hold more progressive political views, on average, than those living in detached homes.
Three-quarters of those in apartments say government should spend more money improving social services, even if doing so results in a budget deficit. Four in five apartment dwellers also think governments should "make changes" in social policy in areas such as euthanasia, relaxing laws on illicit drugs and reduced incarceration rates and jail terms.
"Politicians must pay attention to the various demographic groups who live in apartments as they can have a different political preference from house dwellers," Mr Johnson said.
"As suburbs increase the number of apartments as a proportion of all homes, it is likely that the voting preferences will change."
