Fire safety evaluation is rarely involved in the iterative building design process except for legislative approval phases compared to other building objectives. However, regardless of architectural design priorities, all buildings should have adequate fire protection. This research develops a fire vulnerability assessment model based on the impact of architects on fire protection and effects of building design characteristics on fire safety. Inherent to the uncertain nature of fire safety evaluation practice, this study proposes a fuzzy vulnerability decision-making methodology to detect and visualize escape route vulnerabilities, which have the highest impact on the interoperability of fire safety and architectural design practices. The model was validated in an opera house building since the assembly occupancies have specific importance due to the significant number of fire causalities. The escape routes of the case study building were evaluated for materials' fire reaction, route flow, route equipment, means of egress, dimensions and layout input variables. The output vulnerability levels were discussed to enhance the understanding of critical building design factors that contribute to fire vulnerability. The results confirm that the model is fairly effective in the detection and visualization of vulnerability sources by reducing communication time delays and preventing human-induced mistakes.