AUSTRALIANS have more and more bedrooms, but more and more of them are empty. The latest housing survey by the Australian Bureau of Statistics finds us with more unused bedrooms than ever and less likely than ever to own our homes outright.

Traditionally one of the world's highest, Australia's rate of outright home ownership has slipped from 42 per cent to 33 per cent in the past 15 years. At the same time, the proportion of households attempting to buy with a mortgage has climbed from 30 to 36 per cent, and the proportion renting privately has climbed from 18 to 24 per cent.

The changes follow new tax rules that made negative gearing more attractive from late 1999, increasing the number of landlords and pushing house prices beyond the reach of many would-be home buyers. The ABS says the average first-home-buyer loan climbed from around $160,000 to near $280,000 between 2001 and 2011.

The ABS says the slide in outright home ownership may also reflect the increasing use of redraw facilities, which allow borrowers to top up rather than pay off their mortgage.

There's certainly more room per person. Over the past 15 years the number of people living in private houses has climbed 23 per cent. The number of houses has climbed 28 per cent. The average household size has slid from 2.7 to 2.6 people, but the average number of bedrooms has climbed from 2.9 to 3.1.

''Households on a single wage would struggle to pay $460 a week, which is the new median cost of first home buyers,'' said Sarah Toohey, campaign manager for Australians for Affordable Housing. ''They are having to question other financial decisions … and they are increasingly vulnerable to life changes.''