Josef Žák became a builder “by the decree of the Imperial-Royal Viceregency of 18 June 1896 and by the magistrate’s assessment of 7 July 1896”. At that time, he lived at 1642/2 Hálkova Street in Prague’s New Town. He designed buildings and was active in building construction. In 1898 he took part in the exhibition of architecture and engineering in Prague, where he received the silver medal of the City of Prague.
Žák also took part in project competitions. In 1898, for example, he came third in a competition for the design of a realschule in Náchod. In 1899, he designed a school building in Kukleny, Hradec Králové, which he later built together with Filip Trdlica.
Josef Žák also worked on a number of projects in Prague, mainly as a co-author of designs or as a builder of designs by various architects. He collaborated with architects Antonín Engel, František Velich, and Osvald Polívka.
Denisa Römerová, Vojtěch Škuta, Dominika Dobiášová
Pavel Vlček, Encyklopedie architektů, stavitelů, zedníků a kameníků v Čechách. Praha: Academia, 2004. s. 735.