The intense competition imposed by the current global market, forces companies to implement lean manufacturing techniques. Major progress has already been made in this field and factories continue to reduce costs and lead times. Within this context, the crucial impact of logistics on production efficiency renders the design and planning of the supply chain a key factor in the reduction of costs and the maximisation of product availability. The logistics of an assembly workshop are usually specified empirically, which often generates an overestimation of its needs. Therefore, the current study focuses on these needs and introduces the ACW (assignment of components in warehouses) method for optimising the assignment of components to storage areas. This original method is based on a successive resolution of cost assessments, shortest path problems and generalised assignment problems. It takes into account congestions in the network of aisles that appear during the loading/unloading stages of material handling. A case study of Renault's Flins factory is detailed to validate the proposed method.