The demand for multi-story timber buildings is rapidly increasing due to key factors such as lower costs of realization, high level of prefabrication, and growing environmental awareness. This work focuses on evaluating the dynamic properties of two multi-story Cross-Laminated Timber (CLT) buildings. The selected buildings are two identically realized eight-story residential buildings, part of the Kvarter Limnologen in Växjö (Sweden). At approximately 15 years old, Kvarter Limnologen is among the oldest CLT buildings and is entering a new stage in its life cycle.

To evaluate the modal parameters, three sensor layouts were used during ambient vibration tests. In the first configuration, four sensors were placed on the top story to capture preliminary modal parameters. The second layout increased the number of sensors to twelve, alternating across floors to improve the spatial resolution. Finally, a multi-setup approach was adopted to achieve more accurate mode shapes, using a roving accelerometer configuration while keeping the sensors on the top floor as reference.

The results demonstrate that an optimized sensor placement strategy for multi-setup modal testing allows the evaluation of detailed information about the dynamic properties of the two buildings. The current modal properties—natural frequencies, damping ratios, and mode shapes—of the two building were compared with the results obtained a decade ago. The findings provide valuable insights into the long-term behavior and performance of CLT modular structures, supporting the development of effective structural health monitoring methods.