The business building that exists since 1989 and contains several medical and other offices over five floors needed to be renovated because the concrete of the highly stressed support components of the underground car park had been substantially corroded by the changing humidity. Hence, the stability of the building could no longer be guaranteed. PTI AG as general planning company was charged with establishing an expert statement regarding the support elements leading to their renovation. Afterwards, a limited call to tender / procurement as well as construction supervision were performed.