The seismic vulnerability assessment of the existing building stock poses major challenges with tremendous economic and societal impact. While advanced and well-enforced building codes remain the backbone of risk mitigation, large parts of the European building stock have been built prior to modern building codes and thus, do not comply with the current seismic standards. Furthermore, the seismic assessment of individual structures suffers from large uncertainties pertaining to unknown material properties, soil-structure interaction and unpredictable effects of ageing, while the current state of practice for urban-scale vulnerability assessment relies on heavily simplified physical models. To this end, Structural Health Monitoring (SHM) provides tools for the interpretation of structural-response measurements in order to gather information on the structural condition. Measurement data can further be utilized to update computational models with the goal of refining seismic-performance estimations. In this contribution, the impact of amplitude-depended model updating on the expected seismic performance of an existing masonry building is assessed. Dynamic recordings under ambient excitation are analyzed and compared to the response to higher amplitude vibrations, which are generated during demolition works. Special consideration is given to the analysis of amplitude-dependent properties that are shown to substantially affect the response in the nonlinear range. Overall, this contribution aims to highlight the significance of SHM-based model update for the reduction of uncertainties in seismic risk assessment of individual structures that are representative of common building typologies in places of moderate seismicity.