The ACT assembly passed a $762 million appropriation bill to pay for the scheme on Thursday, and Chief Minister Katy Gallagher said as many as 28 of the Fluffy homes could be in government ownership by Christmas.

In January, pilot demolitions of some of the five public housing properties in the Fluffy cohort will begin, allowing the government to test demolitions of double-brick and brick-veneer homes.

Ms Gallagher said it was an "unprecedented scheme in the ACT and in the world", and would bring a permanent end to an asbestos legacy that had plagued the city for half a century. Its costs and complexity would test the government, its budget and the community but it offered safety, fairness and certainty.

Planning Minister Mick Gentleman revealed proposed changes to the Territory Plan to reduce the block size for Fluffy-block dual occupancy, and to allow Mr Fluffy dual occupancies to be sold as separate titles. At present, blocks bigger than 800 square metres can have dual occupancies but they cannot be sold as separate titles.

Mr Gentleman said 863 Fluffy homes were in the standard RZ1 residential zone. Of those, 567 were on blocks bigger than 800 square metres, and another 204 were on blocks of 700 to 800 square metres.

The proposed Territory Plan variation would allow them to be carved up and sold as separate titles but Mr Gentleman said the government was considering a new safeguard – that the homes be designed by an architect. He also stressed that dual occupancies had a maximum plot ratio of 32.5 per cent, which was less than the 50 per cent allowed for a single dwelling, and needed development approval.

Fluffy owners have argued for the option to keep their land, rather than having to buy it back at an inflated price when it has been cleared and readied for dual occupancy. But Ms Gallagher rejected the call, saying she could not abandon the only part of the scheme that allowed the government to recoup some of the enormous costs.

Ms Gallagher said Treasury modelling suggested it would cost an extra $55 million to allow residents to keep their land. When it was already asking the community to shoulder $300 million to $400 million to pay for the scheme, she could not wave away another $55 million.

But she insisted the scheme was flexible. Older residents and others not ready to leave could stay for up to five years. Where families planned to buy back their land, the government would try to preserve trees, subject to the overriding aim of removing contamination.

For families worried they could not afford to buy land back (and with a household income of up to about $160,000), the land-rent scheme could help.

But the homes could not be made safe to live in. About 10 per cent were so badly contaminated they were uninhabitable. Fibres had been detected in the living areas of 50 to 60 per cent of homes. Families and friends no longer visited, access to trades was becoming prohibitively expensive and health workers were refusing to enter. The government would organise invasive tests where families had claimed there was no Mr Fluffy.

But the Liberals' Jeremy Hanson said the scheme was neither fair nor flexible.

He supported the need for the homes to be demolished eventually, but said residents felt like they had a gun to their heads in a scheme that was supposed to be voluntary.

"The consequences of joining the government scheme is that they are driven from their homes, they are driven from their blocks, they are driven from their communities and that, Mr Speaker, is not fair," he said.

He had spoken to a couple who had been in their home for 64 years and the inability to return was a tragedy, he said. If the elderly had not contracted an asbestos-related disease after decades in their homes, they were unlikely to do so now, and even if they did, being forced from their homes would be just as bad.

The October 28, 2014 valuation date was not fair, given that the market was now inflated by hundreds of Fluffy owners trying to buy in desperation.

"The home that was going for $550,000 a couple of months ago is now going for $650,000," he said.

Mr Hanson said while there was a cost to his suggestions, looking after Canberrans hit by a tragedy such as Mr Fluffy should be the government's No 1 priority.

Asbestos Taskforce head Andrew Kefford said valuations had been received for 28 homes but offers were yet to be put to the families, who can pay for another valuation and review if they are not happy.