Our company undertook the preliminary structural assessment of an existing building in Kolonaki, as part of the investigation into its structural vulnerability under seismic actions. The scope included a structural survey and an on-site investigation, involving the use of a scanner to identify reinforcement, as well as the recording of the structural members’ reinforcement details, based on the available drawings of the approved structural design. Detailed calculations were carried out for the critical characteristics of the structure, including the Centre of Rigidity and the Centre of Mass, in order to assess the building’s seismic sensitivity, its regularity in plan and elevation, and the likelihood of unfavourable structural behaviour under seismic loading. These characteristics, combined with the results of the structural survey and the recorded pathologies of the building, were used to classify the structure into a priority category for further investigation, in relation to its seismic vulnerability, in accordance with the D.E.D.O.T.A. form (Structural Vulnerability Assessment Form). The project was completed with the preparation of a full set of structural survey drawings, a detailed structural calculation report, and a technical report presenting the calculation results and the main conclusions regarding the structural condition of the building and its priority category for further investigation.