Theoretically, it may be assumed that with proper construction and maintenance the life of a building could be extended almost indefinitely. In practice, however, buildings tend to have a finite lifespan. The performance of the building in relation to functional use to meet current needs often determines the usability of the building. Objective measurement of functional performance in a building is a very complex issue. Although some functional attributes can be expressed in quantitative terms, it is not possible or practical to express all functional attributes such as safety, security, convenience etc. in quantitative terms. In this paper, the development of a PC-based computer model to assist in the measurement of functional performance of a building is discussed. Buildings possess complex sets of attributes and most of the attributes are interdependent. Measurement of the functional condition of a building includes comprehensive evaluation of the attributes in relation to each other.