Was born in Amsterdam, Netherlands, where he was educated and apprenticed to the Amsterdam City Architect. He arrived in Johannesburg in 1889 and was recommended for a post as an architectural assistant in Johannesburg in 1889. He appears to have been employed by the Departement van Openbare Werke, Zuid-Afrikaasche Republiek for several years, (a number of payments for travel were paid to him by the Department. He worked in partnership with F SOFF from about 1895 to about 1923 in Pretoria (cf DE ZWAAN & SOFF), after which he seems to have practised on his own account. Having married in 1898 and settled in the city he remained in Pretoria all his working life, his obituary noting that he had worked there for sixty years. However it is recorded that he was deported without reason as a foreigner (Ploeger, 1990 23:30) when the British forces took Pretoria in 1900. He must have returned after the war. At the time of his marriage he was living at erf 233, Celliers St, Muckleneuk. He was responsible for two of the buildings on Church Square, Pretoria, the old President Hotel (renamed The Grand Hotel), a three-storeyed building with verandahs on each floor, and the well-known Nederlandsche Bank building. This latter building was saved from demolition following public protest in 1975. De Zwaan appears to have worked in association with the South African Township & Mining Company who developed the suburb of Waterkloof, he designed houses in two's in the area between the Pretoria Country Club, Main St, Premier St and Lawley St around 1904. Most of these houses still exist although most have undergone alteration which makes them less easy to identify. They had the following features in common - tin roofs with peaked wooden ventilation openings, shuttered, wood-frame windows with small panes and entrance stoeps, the larger houses in Albert St having columned stoeps. He is said to have been a 'big, aristocratic Hollander' (Du Plessis 1990), and his houses reflect this; his nickname was 'Zwaantjie' and he was also known as Wim. De Zwaan was elected to the provisional council of the newly-formed Association of Transvaal Architects in 1911 in order to deal with the Architects' Act (Transvaal) of Registration. He lived latterly at 'Therapia', Albert St, Waterkloof, Pretoria, in a columned colonial-style house of which he was the architect.
He may have designed Rissik's house, Linschoten, Park Drive, Pretoria, which has been attributed to him (Picton-Seymour 1977:301); he is said to have been the architect for Sammy Marks's house at Zwartkoppies with one VAN DYK in around 1898- with whom he is listed in partnership in the General Directory of South Africa for 1898-1899 (cf VAN DYK & DE ZWAAN). The Nelmapius house at Irene is of the same informal colonial style, verandahed with large, high rooms as was his style. De Zwaan was the architect of two 'summer houses' at Zwartkops, south of Pretoria for the families Van Boeschoten and Lorentz. House Van Boeschoten is surrounded on three sides by a wide, columned stoep, two Dutch gables at roof level define the shape of the house. Its proportions and generous if eccentric planning provide an atmosphere of serenity and space which sooner or later becomes a trade-mark of a De Zwaan house.
Both De Zwaan and SOFF are recorded as members of the Pretoria Club in 1903 and were jointly commissioned to design the additional wing to the Vermeulen Street facade (eastwards extension) (Atkinson, 1969).
It is of note that Sir Percy Fitzpatrick chose De Zwaan as the architect of his house in Parktown, Johannesburg (c1912), now demolished, since he could have chosen one of a number of fashionable Johannesburg to design it. This double-storeyed house was a simple, stuccoed square building with few embellishments. A quantity of diaries, papers and memorabilia belonging to De Zwaan was burnt after his death, so study of his career is difficult.ISAA 1927. (Afr Archt Jun 1911:21; Dunston 1975; General directory of South Africa 1898-99; ISAA mem list; PAS Newsletter no 2 1986; Picton-Seymour 1977; Restorica 8 1981 (*?); SAAR Dec 1948:33, 340 obit; SAWW 1911, 1916; TAD MHG 4768/48; TAD SS/r1 614/89)
All truncated references not fully cited in 'References' are those of Joanna Walker's original text and cited in full in the 'Bibliography' entry of the Lexicon.