In the first half of the 20th century, Josef Jihlavec was one of the leading builders in Hradec Králové, shaping modern city architecture and its construction qualities. Jihlavec came from a Protestant family of a small farmer. As a licensed architect and property developer, he initially resided at 305 Eliščino Embankment in Hradec Králové. After apprenticeship, he studied at the Department of Civil Engineering at the Technical College in Liberec. In 1899, he married Vladimíra Zimmrová of Rychnov nad Kněžnou. They had two sons (Josef, born in 1903, and Jiří, born in 1904) and a daughter (Věra, born in 1900). On 4 June 1921, Věra married businessman Josef Voženílek of Předměřice nad Labem who owned extensive plots of land and asked Oldřich Liska to design the first private hydroelectric power plant in the Hradec Králové region. The power plant worked until 1932, when it was pulled down by a devastating flood. In 1900, Josef Jihlavec became a builder. His company first constructed several factory buildings. In 1909–1913, they did the masonry work on the museum designed by architect Jan Kotěra, while concreting work was carried out by František Jirásek’s company. As evidenced by historical documents, there was a lot of competition and animosity among the builders which led to delays in construction work. In 1914, Jihlavec’s company resided in a representative residential building at 556 Československé armády Street, designed by Bohumil Waigant. Between 1901 and 1941, Jihlavec’s architectural firm constructed 32 larger buildings in Hradec Králové, for example, two power plants on the Orlice River, the Paříž Hotel, and a food production factory for Katschner Company. During the post-war emergency in 1919, Jihlavec joined other local builders, engineers and bricklayers to found the Association of Builders and he became its chairman. The Association built 44 municipal and cooperative houses and the workers’ Střelnice cinema. Outside Hradec Králové, it constructed 36 buildings, mainly industrial buildings as well as schools in Vamberk and Pecka, and a Sokol gym in Třebechovice. In 1925, Josef Jihlavec supervised the construction of lower secondary schools designed by Josef Gočár, although the responsible builders were Josef Vyleťal and Josef Novotný. Jihlavec’s collaborators included well-known architects such as Oldřich Liska, Bohumil Waigant, and Vladimír Fultner. In 1928, Jihlavec asked Bohumil Waigant to design a second house for him. In 1936, Josef Jihlavec was also involved in the local competition for the redevelopment of the historical city centre, which was never put through. His license was cancelled on 10 July 1947.