The design of a manufacturing layout is incomplete without consideration of aisle structure for material handling. This paper presents a method to solve the layout and aisle structure problems simultaneously by a slicing floorplan. In this representation, the slicing lines are utilised as the aisles for a material handling system. The method decomposes the problem into two stages. The first stage minimises the material handling cost with aisle distance, and the second stage optimises the aisles in the aisle structure. A representation of slicing floorplan is introduced for the optimisation by genetic algorithms (GAs). The corresponding operators of the GA are also developed. Computational tests demonstrate the goodness of the method. A comparison study of the GA and the random search (RS) for the problem was performed. It showed that the GA has a much higher efficiency than a RS, though further study is still needed to improve the efficiency of the GA.