[1] Walter Burley Griffin was born near Chicago and trained at Nathan Ricker's School of Architecture at the University of Illinois, graduating in 1899.

In 1911, Griffin married Marion Mahony, who had graduated in architecture from the Massachusetts Institute of Technology and worked as Wright's head designer.

[1] By 1914 Griffin and his architect wife Marion Mahony had moved to Australia after winning the 1912 international design competition for the Federal Capital, Canberra with a scheme based on its topography, a distinctly non-prairie valley landscape of undulating hills.

He also developed an economical construction system of pre-cast interlocking structural tiles, which he called "Knitlock", and used it widely, as well as stone, in the houses of Castlecrag.

[2][1] Griffin's contribution to the development of the Wrightian / Prairie School style internationally has begun to receive attention from architectural historians in recent years.

It is now increasingly acknowledged that Griffin contributed a number of fresh concepts to the Prairie School, most noticeably: his attention to vertical space (a development leading directly to the ubiquitous split-level style post-war houses); "open plan" living and dining areas dominated by a large central fireplace; and the extensive domestic use of reinforced concrete.

[7][1] Griffin is also internationally renowned for his work as a landscape architect, especially the innovative town planning design of Canberra and Castlecrag, Griffith and Leeton.

Landscape itself, for example, crucially served as a basis for architecture - a conviction first made explicit in the Canberra publicity, Griffin noting (in Chicago) that: "...a building should ideally be "the logical outgrowth of the environment in which [it is] located"."

Scottish castle themes in the area were already evoked in the Gothic stone bridge, built 1892, between the suburbs of Cammeray and Northbridge, and at the previously named "Edinburgh Rock" on the Castlecrag peninsula.

[1] The indigenous people of the area were Kurinngai or Gurinngai speaking groups, probably affiliated with the nearby Cammeraigal community or the Gorualgal settlement at Fig-Tree Point close to Middle Harbour.

[10] Kurinngai groups lived for thousands of years successfully utilising and managing the area's rich resources of fish, mammals, birds and vegetable products.

Reminders of the Kurinngai's original occupation are evident in the landscape around Middle Harbour: middens, scarred trees, initiation sites, and especially dramatic rock carvings.

Up until 1879 an Aboriginal group was living at the west side of Circular Quay, but at that time the people were relocated to La Perouse.

Communal walkways and reserves were included, and community activities such as dance classes, concerts and neighbourhood meetings were encouraged.

Banks would not lend for his designs which made construction of the dream community difficult, and less than two dozen houses out of potentially several hundred were realised in the planned form.

[1][9] The design of the houses emphasised use of stone and sand-coloured concrete, mostly low to the ground, mimicking and complementing natural earth forms.

[11] Over the decades Frank Duncan and his family added some extensions to suit their needs: a bedroom, a garage, and loggia (outdoor covered patio area), modest in scale, and in materials harmonising with the original house.

Mr Duncan supported the idea, and government bodies gave indications that if a locally formed group would operate the museum, then funds could be made available for its purchase.

Closeness to the garden and nature were integral elements of the house design, and Walter Burley Griffin himself contributed specimens of Australian flora for planting throughout Castlecrag.

Chevron motifs and vertical fins are also characteristic of the Inter War Art Deco style, but Burley Griffin's use of rusticated stone and his philosophy of creating a building in harmony with the landscape resulted in a fusion of grace with earthy ambience at the Duncan House.

[20] The building has a square bedroom extension added to the rear of the house, designed by Eva Buhrich and sympathetically constructed in 1943 from unpainted blocks of concrete with plain painted timber window frames.

The house is a diminutive yet perfectly proportioned example of W B Griffin's work, using his patented knitlock concrete, ribbed and gracefully crenellated, yet grounded in the earth through the use of heavy rusticated protruding stone corner piers.

The chevron motif french doors open to the garden in close proximity, modeling methods of home building several decades ahead of later popular trends.

[1] The house has social significance for being associated with the Griffins who also lived in the Castlecrag community, and for being the home for over 50 years of Mr Frank Duncan.

[1] When Mr Duncan planned to move away from the house in 1988, he indirectly inspired the formation of the Walter Burley Griffin Society.

They were unsuccessful but the house has social significance for having inspired the work of the Society who have subsequently contributed to the appreciation and understanding of the Griffins' vision and importance.

The Griffin-conceived Castlecrag area subdivision is historically significant at state level for its innovative goal of working with natural landforms and flora rather than against them.

Griffin was the designer of Australia's capital in Canberra, as well as dwellings and public buildings in Melbourne, Sydney, the United States and India.

[1] The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales.

The house is aesthetically significant as a visually delightful and intact at date of listing interpretation of Walter Burley Griffin's vision for buildings in the Castlecrag area.