Of 124 submissions on the plan to rezone, only about 10 support it, with the rest strongly opposed, saying allowing higher density development across the city's suburbs would hit house values and lifestyles, and cause over-shadowing and increased traffic. They also complained about poor planning, given the only reason for subdividing Fluffy blocks was so the government could make more money from selling the land.

"If zoning and building envelopes are to be altered, it shouldn't be according to a completely random factor like whether previous homeowners had loose-fill asbestos pumped into their homes," submitter Gareth Davies wrote. "You might as well just throw darts at a map and draw proposed amendments out of a hat."

"It is hoped that the ACT government will think long and hard before hastily approving dual occupancies here, there and everywhere," Pearce residents Steve and Dianne Flora wrote, warning against "short-term profit blindness".

Aranda resident Jean Geue said it was "the cut of a thousand deaths to Canberra's well-designed suburbs", and the government should bear the cost, rather than "trying to make a small gain out of community misery".

Fluffy owners wanting to return to their blocks and rebuild also opposed the change, Hackett residents Alison Thomson and Lincoln Smith saying it would force them to pay more for their land "due to development potential that we have not requested and have no interest in realising".

Lyons resident Catherine Caruso said she faced paying more for her land and higher rates. The change was also contradictory, with the government planning to reissue leases for cleaned Fluffy blocks so they no longer referred to asbestos, but the different planning rules identifying them immediately as Fluffy blocks and leaving them forever stigmatised.

Many residents complained the planning change was being made while the list of Fluffy homes was still a secret, making it impossible for people to know whether next-door blocks were slated for redevelopment.

But builder groups and architects largely supported the move, while urging changes to plot ratios and height restrictions.

At the moment dual occupancy is allowed on 800-square-metre residential blocks, but the two homes can't be divided into separate titles. The change will reduce the minimum size for Fluffy blocks, allowing dual occupancy on 700 square metres, and also allow the two homes to be strata titled and sold separately. Fluffy dual occupancies will be allowed to cover 50 per cent of the block if both homes have direct street frontage, and 35 per cent otherwise. Two-storey homes will be allowed if both homes have direct street frontage; otherwise the limit will be one storey.

Glen Dowse, of Dowse Norwood architects, said the city must looked inward to higher density and reinvigorating old housing stock, providing opportunities for young families to move in. While a 700-square-metre block was difficult for successful dual occupancy, it could be done with quality design, he said, urging the government to abandon the 35 per cent plot ratio, allowing 50 per cent for all of the blocks. The street frontage restrictions should also go, and trees in the blocks should not be protected if they were planted by the owner, he said.

Architect Alan Morschel said the change was "sensible and visionary", and given it would only affect a few hundred sites it "should be a demonstration to the many nimbys that their suburban dream will not be ended by the erection of a few more houses". Instead, the new neighbours would add to the diversity and richness of the community.

"Single-fronted blocks ... will have difficulties meeting the design criteria on 700 square metres with only a 35 per cent plot ratio," he said.

The Master Builders Association said the move would help a struggling building industry, but the planning change should be extended to all suburban blocks, not just Fluffy ones.