In this work, we propose a method and its concomitant software for the identification and assessment of building-evacuation routes. First, the building floor map is represented via P-graphs, thereby facilitating the identification of the evacuation routes. Second, each route identified is transformed into a time-expanded, process-network synthesis (PNSt) problem, which can be algorithmically solved by the P-graph methodology. In the proposed method, each location and passage in the building is defined by a set of attributes to be taken into account in the evacuation-route planning. Third, the evacuation routes are ranked in terms of the evacuation time computed as the minimum cost of the corresponding PNSt problem. Furthermore, the evacuation routes can be ranked according to specific criteria (e.g., bottlenecks, route utilization, etc.).