Publisher Summary The requirements of building structures are likely to change during their functional working life. Therefore, designers of building structures should strive for the best possible match between technical service life (TSL) and functional working life (FWL). This chapter presents industrial, flexible, and dismountable (IFD) building as a design approach for building structures to deal with these aspects. The IFD concept combines sustainability with functionality and results in higher quality level of buildings. The IFD design approach leads among others for the integration and independence of the disciplines. Timber floor system makes use of the neutral zone of the floor to accommodate technical installations. This chapter also describes the composition of the integrated timber floor system, and focuses on the dynamic behavior and fire safety of this lightweight floor system.