Torrential rain has lashed Queensland and New South Wales in the wake of Cyclone Debbie.
A woman and her two children were plucked from their roof after spending hours waiting in the dark for help.
The house broke away about 15 minutes later, a Queensland State Emergency Service spokesperson told the BBC.
Neighbours had called authorities to the scene at Luscombe, in Queensland's Gold Coast hinterland, on Saturday.
"It took us approximately an hour to dodge the high trees, the power lines, the stuff that was coming down the river," one rescuer, Jim Ferguson, told the Australian Broadcasting Corp.
Fellow rescuer Chris Holloway said he was relieved the house did not give way earlier.
"We've gone through all these 'what ifs', because after the rescue we were stranded there for a good four hours before we could get another rescue team in to help us," he told the Brisbane Times.
The building crashed into another house before hitting trees and breaking up, he said.
An Australian family was rescued from the roof of their house minutes before it was carried away in floodwaters, authorities have said.