The size of Australian homes is plateauing, while homes in the US keep growing, according to CommSec's Home Size Trends Report, which examines specially commissioned Australian Bureau of Statistics data.

The average floor area of a new house built in Australia in 2015/16 was 231sqm, down from a record 248sqm in 2008/09, says the report.

The US Census Bureau reports the average size of a new house in the US in 2015 was 2,687 square feet (249.6sqm), or 10 per cent larger than the houses being built in Australia.

Source: CommSec.

The report shows homes in New Zealand are about 7 per cent smaller than homes in Australia, and in Canada are about 10 per cent smaller.

Australian homes are still significantly bigger than they were 30 years ago; the trend towards ever-larger homes sprawling across the Australian suburbs gave rise to the term 'McMansions'.

But that trend seems to be on the decline. In recent years, Australia has been building smaller houses and more apartments. The size of Australian homes peaked three or four years ago, according to the report.

Source: CommSec.

It seems that apartments sizes are shrinking at an even more rapid rate. In 2015/16, the average floor area of a new apartment (a term that includes units, townhouses, villas) in Australia was 131.3sqm, up from 129.0sqm in 2014/15, but almost 9 per cent lower than the high of 143.7sqm in 2004/05.

Source: CommSec.

The decline in home sizes is in line with the decline is the number of people per dwelling. In 1911, there was an average of 4.5 people in every home, while in 2006, the year of the last census, the ratio was down to 2.4 people per home.

But between 2006 and 2013, that trend reversed, with the number of residents per household increasing, as children tended to stay at home longer and there was a rise of multi-generation living.

But since 2014, the number of residents per household has begun falling again, reflecting smaller family sizes, and the supply of more apartments, which has made young people more likely to move out of their parent's home, and elderly people more inclinded to downsize.

Victorians are building the biggest houses in Australia, with an average house size of  241sqm, ahead of Queensland with 238sqm, NSW with 227sqm, and Western Australia with an average house size of 227sqm.

The report highlights the complexity of the data in identifying if the flood of new construction in the last few years is in danger of reaching oversupply. "Clearly the issue of over-supply is complicated. But the changes in housing demand and supply have major implications for builders, developers, investors, building material companies, financiers and all levels of Government," the report states.

See also:

Block sizes are shrinking, and land prices are rising

Let's focus on design, not size, with apartments

Are new apartments too small?