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Selecting an appropriate flooring system is essential for structures. Flooring system design has traditionally focused on weight loss and minimizing costs. However, in recent years, the focus of this sector has changed to include improving the environmental performance of building materials and construction systems. This paper illustrates a knowledge-based expert system as a tool to assess of flooring systems such as block joisted (BJ), steel-concrete composite (SCC), composite steel deck (CSD) and concrete slab (CS) based on sustainability criteria that are further divided into twenty sub-criteria. Analytical hierarchy process (AHP) is utilized as a multi-criteria decision making technique that helps to compute weights and rankings of sustainability criteria. For this purpose, some questionnaires completed by construction industry experts in order to compare criterions and sub-criteria in addition to assessment of optimized flooring systems. Then, results of the questionnaires are ranked by AHP and the most significant alternative is selected. The AHP results indicate that CSD system 47.9%, CS; 29.8%, SCC; 12.7% and BJ system 9.6% are the most and the least efficient systems, respectively.