Homeowner Erin Hunt, spokeswoman for the Mr Fluffy Full Disclosure group, told a committee considering the plan to allow dual occupancy on land bought back by the government that splitting blocks was akin to "throwing darts at a map of Canberra" under the guise of meaningful government planning.

Some of the group's more than 400 members believed dual occupancy would weaken quality of life in the city's suburbs and see some residents living without enough space, while also creating inconsistent planning rules for properties side-by-side.

"Basic common sense tells us that there should not be different rules for blocks within the same zone," Ms Hunt told the committee's first public hearing.

"If the proposed changes are not consistent with the zoning objectives then the ACT government should abandon them. The government's position is indefensible, we believe. Approving these changes could set a precedent for other [suburban zoned land] owners to seek additional permissions for their blocks."

In a sometimes tearful statement, Ms Hunt said the government's Environment and Planning Directorate had told the committee that unit titles for suburban-zoned houses, known as RZ1 blocks, supported a range of low density housing choices.

"If this argument is valid, then why are the provisions not being extended to all RZ1 blocks? The directorate fails to explain why it is appropriate for these changes to be made only to RZ1 Fluffy blocks and not all of the RZ blocks across the city," she said.

The suburban zoning covers more than 80 per cent of all residential land in the ACT but the changes are only proposed for blocks being purchased in the Fluffy buy-back scheme. The zoning allows for low rise and predominantly low density housing, the majority of which are single residences.

The government proposed the Territory Plan change in an effort to maximise sale prices for land from demolished loose fill asbestos homes, helping to offset the cost of buying and demolishing more than 1000 contaminated homes.

Planning officials recommended the plan go ahead but it was sent to the committee for consideration by Planning Minister Mick Gentleman in July.

Ms Hunt said suburban infill and increased density required better consideration of issues including transport, traffic, schooling, access to amenities and services.

"Economic outcomes... must be balanced with social and environment outcomes. Mr Fluffy owners are part of the community, we pay our rates, most of us still live here and all of this relates to us as part of the community," she said.

The committee also heard evidence from Master Builders Association deputy executive director Michael Hopkins, who said allowing dual occupancy would see more housing stock built in the Canberra market, benefiting local builders and would help relieve a "chronic shortage" of land for new homes.

He said Canberra would benefit from sensible and measured urban infill development and more diverse housing stock.

Evidence was also received from the Weston Creek Community Council and the ACT Housing Industry Association.

Fluffy home and Woden Community Service director Chris Redmond said on Wednesday that the community response to the buy-back scheme had been similar to the response in the wake of the 2003 bushfires.

"While it is not as apparent as with the fire where you could see the devastation and the loss of homes …I think the Canberra community has recognised that it is a community issue," he said.

"I am quite amazed by the generosity Canberra community of in terms of seeing it engage with the response of home owners."

Mr Redmond, who is a member of the government's Asbestos Recovery Taskforce, said the territory had been brave in launching the massive buy-back scheme, and taking on large financial costs.

The committee's public hearings will continue next week.