Government and industry groups are collaborating to make homes more user-friendly and enable new fixtures, such as grab rails, to be added without the need for expensive retrofitting.

Wary of price impacts from the new guidelines, Canberra architects and the housing sector are urging the Government not to make them mandatory.

The initiative comes as research has found Canberrans are the most reluctant of all retired Australians to downsize.

Adjunct Fellow at the Swinburne Institute for Social Research Peter Mares has discovered from 2011 Census data that nine out of ten older couples in Canberra live in homes with three or more bedrooms, as do 77 per cent of older singles.

Across Australia 62 per cent of people older than 70 live alone in a three-bedroom or larger home.

Advocates for the ageing say Canberra does not have enough choice of housing stock for retirees to downsize into more suitable accommodation.

Chief Minister Katy Gallagher said the Government was working with construction, housing, community and aged care sectors to make it easier for older Canberrans to downsize.

"We are currently working to deliver more flexible housing options so that our ageing population can downsize without necessarily relocating," Ms Gallagher said.

Australian Institute of Architects ACT chapter spokesman Alan Morschel said residential architects had been adopting the guideline for 12 months.

''Suddenly the ACT Government decides to take the guideline and re-write it as a mandatory requirement for detached housing, which came as a real surprise to us.

''We just do not understand this heavy-handed approach.''

Mr Morschel, who heads the architects planning committee, said members thought the mandatory push stemmed from an agreement between Labor and ACT Greens.

ACT/Southern NSW Housing Industry Association spokesman Neil Evans said about 250 homes in the ACT had taken up the universal design voluntarily.

But smaller homes for first-home buyers would never likely be needed to be retrofitted, so the requirement should not be mandated.

''It will add more dollars and will push first-home owners out of the market,'' Mr Evans said.

The ACT Economic Development Directorate will work with the community sector to identify under-used community facility land for residential redevelopment, including aged care accommodation.

The directorate says residential development suitable for older people in existing suburbs would avoid older people having to leave their neighbourhood to downsize.

The directorate releases land each year specifically for accommodation for older Canberrans. Housing ACT says it encourages tenants to downsize or relocate from larger or "in demand" properties in order to free up homes for applicants in need.

Eleven tenants were transferred under the program in 2012-2013.

The Government has allocated $290,000 for design options for 20 new aged-specific units for older public housing tenants who want to downsize from larger public housing properties and relocate to more appropriate housing.