Design of a day surgery operating room for the XIX. Kispest Health Institute in Budapest with a transformation within the building, without changing the function, in addition to the two small operating rooms operating on the same floor. Due to the limited headroom and the location, the service engineering was placed on the flat roof, with the creation of noise-shielding walls. Due to the design of the operating room according to the standard, a structural transformation was also necessary. All the partition walls of the design area were demolished, the boundary walls of the newly designed rooms are prefabricated structures, fully complying with today's requirements.