The move means the homes will be protected and cannot be altered without first gaining the approval of the ACT Heritage Council to ensure any changes are sympathetic to the style and values of the properties.

Swinger Hill in general was regarded as an experiment in medium-density housing by the National Capital Development Commission and the first 39 homes in Barnet Close were designed by the architects Ian McKay and Partners ''as a prototype to test design principles and as a demonstration project for private enterprise''.

Heritage Council member Duncan Marshall said the heritage listing applied to those homes in Barnet Close because they were the first examples of stepped medium-density housing in Canberra and also pioneered the way for other developments outside the suburban norm.

''And this at a time when a single house on the quarter acre block was thought of as the ideal for the suburbs,'' he said.

The citation for the Heritage Register listing says the collection of homes was the first medium-density cluster housing in Australia to achieve a density of 40 people per acre.

The homes were innovative, provided privacy and individuality while also allowing for communal living and were an alternative ''to the perceived wasteful land consumption of typical suburban sprawl''.

They ''allowed for low-cost living and the design of the courtyard homes with minimal garden freed up time for other pursuits''.

The first five of the houses were opened to the public in April 1972. Housing construction cost the commission $15,000 to $18,000 plus land.

The townhouses appeared to be viewed as such an innovation that The Canberra Times was invited to photograph the finished products, women from the commission, dressed in the fashion of the time, posing artfully in one of the courtyards.

Mr Marshall said the Swinger Hill homes deserved to be on the register as much as items that were considerably older.

''Essentially what the heritage register does is capture the important stories in our cultural history and our natural history,'' he said.

Retired architect Gene Willsford, 90, has lived in Barnet Close for a decade, moving from a larger home in Deakin after long admiring the Swinger Hill design concepts.

''It was the idea of a small block of land with a courtyard. There weren't those great lawns to mow and everything,'' she said.

Brett Odgers, an original Barnet Close resident, says he was excited to move in 40 years ago because he'd been ''frustrated by the open spaces and lack of people'' in Canberra at the time.

But another neighbour, who did not want to be named, was not impressed with the listing.

She said alterations she had made to her property in the past might have to be reversed if she were to sell her home.