Samuel Hurst Seager, the second of four children of Jane Wild and her husband, Samuel Hurst Seager, a master builder, was born in London, England, on 26 June 1855. He emigrated with his parents to New Zealand in 1870, settling in Christchurch where his uncle, Edward William Seager, was superintendent of Sunnyside Lunatic Asylum. His father established himself as a contractor in Christchurch, and after his death in 1874 Seager continued the firm, S. H. Seager, until 1879. In 1877 he constructed the first permanent Canterbury College buildings to B. W. Mountfort's design. He worked as an architectural draftsman for Mountfort and A. W. Simpson, and from 1879 to 1882 studied at Canterbury College. Seager's knowledge of Gothic Revival design principles and appreciation of the importance of architectural tradition are attributable to Mountfort's influence.
Between 1882 and 1883 he studied architecture in London at University College, the National Art Training School, the Architectural Association and the Royal Academy of Arts. An exceptional student, Seager was invited to lecture at the National Art Training School in South Kensington in 1883 and 1884. He became an associate of the Royal Institute of British Architects in 1884 and was made a fellow in 1907.
After a period of travel in Europe he returned to Christchurch well versed in the latest developments in European architecture. His 1885 competition-winning design for the Christchurch municipal buildings introduced the newly fashionable Queen Anne style to New Zealand and established Seager as one of Christchurch's leading architects.
On 16 December 1887 Samuel Seager married Hester Connon at the home of her sister, Helen, and brother-in-law, Professor John Macmillan Brown, in Fendalton, Christchurch. There were no children of the marriage. After a brief period in Sydney (from 1891 to 1893) he became a lecturer in architecture and decorative design at the Canterbury College School of Art and continued in this position until 1918. He served on the college's board of governors from 1910 to 1919 and his 1913 scheme for the completion of the college buildings played a decisive role in ensuring that the complex was architecturally coherent.
By 1900 Seager was recognised in New Zealand as a leading designer of large houses in the English Domestic Revival style. Such houses are found throughout Canterbury, the best example being Daresbury in Christchurch, built for George Humphreys between 1897 and 1901. Seager's own house in Cranmer Square, which he bought and extended in 1899, paid tribute to his architectural mentor by quoting motifs from Mountfort's Christchurch Club, designed in 1859. It also demonstrated that colonial buildings could inspire a local architectural tradition. Seager regretted the absence of this tradition, and in 1900 published his views in an influential article, surveying the development of architecture in New Zealand.
The timber cottage built at Cashmere for the Macmillan Browns in 1899 revealed the influence of the English Arts and Crafts movement and introduced the bungalow style to New Zealand. From 1902, at The Spur, Sumner, these influences were combined with garden-city planning concepts to produce a unique residential development of timber cottages in a garden setting. Seager lived there until about 1912 when he moved to Hackthorne Road, Cashmere, and designed a unified group of larger scale houses.
Seager was committed to the social role of architecture. He was in partnership with Cecil Wood from 1906 until about 1912 and the workers' dwelling they designed was built as part of the 1906 Heretaunga settlement in Petone, while their model worker's dwelling was exhibited at the 1906–7 New Zealand International Exhibition in Christchurch. Seager was concerned with the total built environment and from 1910 his energies were increasingly directed towards town planning issues, including an involvement with the Christchurch Beautifying Association and the Summit Road Association. The three rest houses he designed on the Summit Road – the Sign of the Bellbird, Sign of the Kiwi and Sign of the Packhorse – approach the simplicity of vernacular structures and seem to grow organically from the landscape.
Seager lectured widely on town planning and the need for appropriate legislation. In 1918 he was the government representative at the second Australian Town-planning Conference and Exhibition, held in Brisbane, and he became the organising director of the first New Zealand Town-planning Conference and Exhibition, held in Wellington in 1919. The success of the conference, and the subsequent enactment of the Town-planning Act 1926, owed much to Seager's foresight, commitment and energy. In recognition of this work he was appointed a CBE in 1926.
Seager campaigned for improved aesthetic standards in First World War memorials, organising a travelling exhibition of model designs in 1920 and writing a government report on war memorials. As official architect of New Zealand battlefield memorials he spent much time abroad from 1920 to 1925. The memorials, designed in 1921 and executed in the following years, include those at Longueval and Le Quesnoy in France, Messines (Mesen) in Belgium and Chunuk Bair at Gallipoli. Each is distinguished by careful siting and austere simplicity of design.
Almost every aspect of architecture engaged Seager's attention. An internationally respected authority on the lighting of art galleries, he was an assessor for the Wanganui and Christchurch art gallery competitions in 1916 and 1929. The winning entries in both these competitions employed the topside lighting system invented by Seager. This system, in which light is reflected onto gallery walls from above, is now used in art galleries throughout the world. A vigorous promoter of professional organisation and standards, he was president of the New Zealand Institute of Architects in 1926 and a member of the council and chairman of the Canterbury branch at various times between 1911 and 1926. He was also a pioneering advocate for the preservation of historic buildings and, as a writer and lecturer, promoted a wider understanding of architecture and its history.
Around 1929 he moved to Wellington. After two years, in declining health he retired to Turramurra, in Sydney, where he died on 5 October 1933, survived by his wife, Hester. Through his wide-ranging activities Seager did more to advance the art of architecture than any other New Zealander of his generation. His most enduring achievements were his awareness that only through planning could a healthy and visually pleasing environment be created, his recognition that New Zealand architecture needed to develop its own identity, and the unpretentious buildings that grew out of this realisation.