Australian capital city home values have hit a record high, driven by accelerating prices in Sydney and Melbourne.
Sydney's median house values rose by 2.5 per cent in September, and Melbourne gained 2.4 per cent.
Still, house values fell in every other major city except Adelaide during September, meaning aggregate capital city home prices rose by 1.6 per cent, RP Data-Rismark figures show.
"We haven't seen market conditions this strong since April 2009 for Sydney and May 2010 for Melbourne," RP Data analyst Tim Lawless said.
Annualised capital gains of 20 per cent in Sydney and Melbourne would be a concern if this continued into 2014, Mr Lawless said.
"If such a high rate of growth continued for a sustainable period, it would have the potential to push home values above what might be considered sustainable market value," he said.
But Rismark chief executive Ben Skilbeck said the likelihood of unsustainably high property prices was still premature, considering that Sydney's long-term growth is modest.
During September, Adelaide enjoyed a 1.1 per cent jump in home prices.
Brisbane prices fell by 0.3 per cent, while values dropped by 0.1 per cent in Perth, two per cent in Hobart, 2.5 per cent in Darwin and 0.7 per cent in Canberra.
Sydney has the most expensive median price tag of $588,000, followed by Melbourne's $525,000.
Hobart has the cheapest median price of $300,000.
Meanwhile, a Housing Industry Association (HIA) survey of Australia's largest builders showed new home sales rose by 3.4 per cent in August, after a 4.7 per cent decline in July.
HIA chief economist Harley Dale said demand for detached houses was rising, but not for multi-unit developments.