The aim of this paper study the impact of class-based storagepolicy basedon the optimal configuration of U-flow single command warehouses using aon an ABC product classification. For that purpose, the authors proposea non linear optimization model to minimize the expected travel distanceof the warehouse and use analytical methods to solve it.The most important contribution is to provide a mathematical proof thatregardless of the storage policy (It does not matter the specifics of theturnover pattern of the products), the optimal warehouse has a width thatis the double of its length, and the pick and deposit point should be locatedin the middle of the width of the warehouse.In addition, authors perform a sensitivity analysis that indicates that theoptimal solution is robust, meaning that a certain deviation from the op-timum layout does not impose a significant penalty on the expected traveldistance of the warehouse.