His work at the Weimar School of Architecture, along with researchers including Karl-Heinz Heuter, contributed to the rediscovery of Bauhaus for socialism in the 1960s.
[12] Flierl gained a doctorate at the Bauakademie der DDR [de] in 1972,[1] and headed the Institute for Theory of Architecture and Urban Planning at the Bauakademie until 1979 and also headed the "Architecture and Fine Arts" working group at the Association of German Architects between 1975 and 1982.
[1] After 1989, Flierl served in multiple urban planning committees focused on the German reunification efforts.
His son Thomas Flierl [de] is an architectural historian and politician who served as counselor for construction for the PDS in Berlin-Mitte in the 1990s, and as Berlin's senator for science and culture between 2002 and 2006.
[15][16][additional citation(s) needed] Flierl died on 17 July 2023, at age 96, in a Berlin retirement home.