In early 1946, UNRRA (United Nations Relief and Rehabilitation Administration) offered to help several European countries, including Poland, to establish production of penicillin. Initially, Poland’s first penicillin plant was to be set up in an old hospital building in Kraków, but experts at the Ministry of Industry found it unsuitable for the purpose. Consequently, the Ministry chose another building, this time an old pharmaceutical factory in Tarchomin, near Warsaw. Disappointed by this decision, the municipal authorities in Kraków commissioned another building appraiser, who after investigating both structures came to completely opposite conclusions. This paper explains how the dispute developed and ponders to what extent the seemingly independent experts become parties in a dispute. This work was made possible through financial support from the National Science Centre, Poland, research grant number 2014/13/B/HS3/04951. Keywords: building appraiser; condition assessment; industrial building; post-war reconstruction.