In the German Democratic Republic, he served as Minister for Construction, Urban Development and Housing of the GDR in the cabinet of Lothar de Maizière.
in 1985 on the topic "A Contribution to Determining 'Favorable' Hydraulic Operating Regimes for Hot Water District Heating Networks in Emergency Conditions or Planned Shutdowns".
[1][2] In 1985, he was made full-time city councilor (member of the municipal government) for energy of Dresden, a position he held until 1990.
[3] After the Wende, the LDP, its new name after being renamed in February 1990,[2][3] joined forces with the other liberal parties in the GDR to form the Association of Free Democrats (BFD).
[1][2] From April to September 1990, Viehweger served as the last Minister for Construction, Urban Development and Housing in the cabinet of Lothar de Maizière.
[4][7] The numerous research institutes assigned to the ministry, such as the GDR Construction Academy, were either be dissolved or transferred to other legal entities by 3 October 1990.
From 2000 to 2002 he was head of the Central and Eastern Europe working group of CECODHAS (Association of the European Social Housing Industry).