Stewart Kaye was born in Park Place, Brechin on 13th July 1883, the second son of James Kaye (d.1929), an Agent for the North British Railway, and his wife Jemima Stewart Morrison (d.1948).  His parents had married in Perth in September 1881.  

He had at least two brothers, Bertram David Kaye, and James Alfred Kaye, who became a Congregational Bishop based in Guildford.

Kaye was educated at Grove Academy and the Technical College and Dundee University.  He trained with Dundee’s MacLaren and Souter and in 1905 moved to Alnwick to become assistant to George Rivell.  Thereafter he moved to Cardiff to work for George WB Rees, and then to JE Rickards in London.  In 1905 he made a study tour to Holland and Belgium and in the following year to Italy. His RIBA obituary claims that he began practising on his own account in 1913, and first settled in Dunfermline where he designed the YMCA Institute in Rosyth in 1915.   He also designed the YMCA in Ayr.

He served as a Lieutenant in the Royal Engineers rising to the rank of Captain by 1918, after serving three years as Garrison Engineer for Edinburgh.  In March 14th of that year he married Mary McKay Ker McGregor (d.1979) at St Georges United Free Church in Edinburgh.  The couple would have at least three children including the architect Ian Stewart Kaye (1919-1987).

He passed the Special War Examination in 1920 and was elected ARIBA later that year, his proposers being Alexander Lorne Campbell, John Wilson and Harold O Tarbolton. He was also a Fellow of the Institute of Chartered Surveyors.

After the war he settled in Edinburgh and by 1922 had an office at 14 Hill Street.  That same year he was appointed Honorary Secretary to the Edinburgh Architectural Association, a role he would occupy for seven years, receiving a wristwatch in recognition in 1929.  
In this role he wrote to the Scotsman in 1922 explaining why there was a disparity in costs in building housing in Scotland, with additional costs related to the Scottish climate and size of houses.

In 1927 he was appointed architect to the District Board of Control at the Gogarburn Institution, the first colony in Scotland built after the Mental Deficiency Act of 1913.  He would design several buildings on the site including the stone-built three-storey administration block, higher grade wards, kitchens, cottages, dormitory and mortuary.

Between the wars Kaye had one of the larger Edinburgh commercial practices, working in what was at times a somewhat strident Art Deco manner. He succeeded to the practice of Robert Macfarlane Cameron on the latter's death in 1921, and about 1936 took George Learmonth Harkness Walls into the partnership. The firm sometimes used Kaye & Walls but by 1945 Walls had set up on his own account.

As consultant architect to the Presbytery of East Lothian, Kaye was involved in major schemes of reorganisation for Yester, Humbie and Dirleton parish churches.  These resulted in quite substantial removal of historic fabric with both Dirleton and Humbie being gutted with much of their galleries and fittings removed.  Chancels were also added. A note on Dirleton was written up for the Scotsman by George L Walls in 1930, and as a former pupil of Lorimer he may have been primarily responsible for the works.

He was also the consultant architect for the private housebuilders MacTaggart and Mickel.  Kaye designed thousands of houses across Edinburgh, specifically at East Pilton, Colinton, and Carrick Knowe.  In the latter development he also provided a stone-built parish church, the hall constructed before the war and the revised design for the church, without tower, began in 1950.  He was not involved with the design of council housing in Pilton with EJ MacRae, (as one report states) but worked closely with the council in the preparation of housing layout. MacTaggart and Mickel’s private homes were assisted by a sympathetic council who helped with the roads, sewers, etc.  Kaye had also worked with MacRae at Gogarburn.  

Kaye was a director of the Dean Property Company and Learmonth Property Investment Company.  These firms developed much of the considerable area between Comely Bank Road and Queensferry Road.   Towards Comely Bank Road are traditional tenements (1935) built in artificial stone, with a distinctive tall stair window which may take reference from the City Architect E.J. MacRae’s work at Saughton (1932).  Kaye claimed the planning of these tenements was influenced by the Highton Report (on Working Class Housing on the Continent) published that year, especially the provision of an open central space behind the blocks for gardens and sports.  
More experimental is Learmonth Court (1936), a six-storey block built in red brick and stone at a cost of £60,000.  It was first mooted as serviced apartment flats in the London style, with a restaurant for residents.  

He was also a consultant to the Halifax Building Society.

Lothian House is perhaps the most significant building designed by Kaye.  It was built on the site of the Port Hopetoun canal basin, and had an estimated cost of £300,000 in 1935.  The building was originally designed as Government offices and was completed in three stages.  The main frontage block, 334ft long, on Lothian Road opened in October 1936, with a Cinema complex – The Regal - to Morrison Street, also by Kaye in 1938, followed by an office block on Fountainbridge, designed in matching style in 1939.

In World War II Kaye again enlisted with the Royal Engineers, but in March 1941 he was appointed Assistant Director for Emergency Repairs in Scotland for the Ministry of Works and Buildings, to help speed up factory repairs. A year later he resigned the post, being replaced by G.Gardner-McLean.

In 1945 he bought Bonaly Tower in Colinton and spent much of his time restoring the building, although never ended up living there.

The practice virtually closed during the Second World War, but after Kaye took his son Ian Stewart Kaye (and Robert Fairbairn Thomson FRIAS) into the firm.

Late in 1951 Kaye invited Colin McWilliam, then just arrived in Edinburgh from the British School in Rome, to assist with the design work as and when his duties with the National Buildings Record allowed.  This arrangement lapsed after Kaye's death.

After the war Kaye was in indifferent health and apparently conscious of being out of fashion.  In his spare time he was a keen golfer and fisherman and also had served as an office bearer for St Georges West Church for 30 years.

Stewart Kaye died suddenly of coronary thrombosis in Belgrave Crescent on 17 February 1952 aged 68.  He left £13,360 16s 19d.

He was buried in Dean Cemetery.

The firm of Stewart Kaye & Partners was dissolved in February 1953.  The remaining partner Robert Thomson also now left but the firm continued under the same name with Ian Stewart Kaye MA ARIBA practicing on his own account.