Staal established himself in 1902, together with Alexander Kropholler (1881-1973), as an architect in his father's Dutch contracting company, Staal and Haalmeyer. Starting in 1903, they designed buildings, which in the beginning were also built by his father's contracting company. Some of the buildings designed by Staal and Kropholler are the offices of the life insurance company "De Utrecht" in Amsterdam and Leeuwarden. In 1910 the cooperation between Staal and Kropholler was broken and Staal started to implement his designs in the style of the Amsterdam School. The villas in Park Meerwijk in Bergen (1917-1918) were his first buildings in this style. Other designs by Staal include the central flower auction in Aalsmeer, a 12-story building nicknamed the "Skyscraper" in Amsterdam, the Dutch pavilion at the Exposition des arts décoratifs et industriels of 1925 in Paris, the main building of daily newspaper De Telegraaf (now the Kas-Bank) on the Nieuwezijds Voorburgwal in Amsterdam, the Koopmansbeurs in Rotterdam, and several houses in the Amsterdam Rivierenbuurt. Not realized was Staal's competition design for an opera house on the Museumplein in Amsterdam: although his entry was preferred in 1920, the opera was not realized. He later used motifs for his flower auction and his Telegraaf building. Staal is a very important Dutch architect who organically evolved from Amsterdam School architecture to New Objectivity. This is clearly seen in the housing blocks in the quadrant Apollolaan, Beethovenstraat, Corellistraat and Bachstraat. The buildings on Apollolaan/Beethovenstraat are characteristic because of the large sleek bay windows, which now also appear modern. The family houses on Corellistraat (even side) also testify to a modern light architectural style. The difference between the architectural style here and that on the J.M. Coenenstraat (also by Staal) is evident and from this its development is clearly noticeable. An ardent socialist, he was also a member of the Communist Party for a short time. Staal was also a board member of the architectural society Architectura et Amicitia for several years. This society held its membership meetings from 1914 in a room in a bank building on Herengracht that he designed. From 1920 to 1930 he was a member of the editorial board of Wendingen. From 1936 Staal was married to architect Margaret Staal-Kropholler (1891-1966), with whom he had had a relationship for much longer and who was initially his collaborator. She was the sister of Staal's former associate Alexander Kropholler. They are buried in the Nieuwe Ooster Cemetery in Amsterdam. His son Arthur Staal (1907-1993) was also an architect and designed the Overhoeks Tower in Amsterdam North in 1966. His son Georges Staal was also an architect and there was also a third son Fred Staal who perished in the Dutch East Indies. A fourth son is the linguist Frits Staal (1930), who, however, has a different mother than Arthur, Georges and Fred. From the marriage to Margareth Staal Kropholler descended a daughter Margareth, or Maggie Venekamp-Staal. In 2015, Staal's 75th year of death, the first monograph on him was published, "Jan Frederik Staal (1879-1940) - The Will of the Building and the Will of Time. The book was written by Hans Willem Bakx and published by the Bonas Foundation.