||Recently, advances in smart sensors and information technology have made building structures more intelligent. In particular, the ubiquitous sensor network (USN) system, which consists of a range of smart sensors and a wireless communication network, is being employed widely as an essential tool to provide a safe and clean environment with a range of applications including automation, fire prevention and security. This paper presents, a smart space test-bed with a built-in USN-based online monitoring system established at Sungkyunkwan University in Korea for both functions of structural health monitoring and environmental monitoring. For the structural health monitoring function, accelerometers, strain gauges, tilt-meters were installed at the host structure and the vibration mode shape, deflection and displacement of a specific member of the host structure were monitored in real-time. Temperature sensors, humidity sensors, CO2 (Carbon dioxide) sensors, windy direction/speed sensors, CCTVs (Closed-Circuit Television) and motion sensors were installed at the appropriate locations for environmental monitoring inside and/or outside the host structure. In addition, all the information obtained from the deployed sensors was collected as a database and an integrated web server which can be connected very easily through the mobile apparatus of the various platforms such as a tablet PC (Personal Computer), a smart phone, MID (Mobile Internet Device), and etc. was constructed. Finally, the built in USN-based online monitoring was integrated with BIM (Building Information Modeling) maintenance for future guidance in ubiquitous environments.