Preliminary design involves the synthesis of potential structural configurations satisfying certain basic constraints. Many of the conceptual aspects of structural design are embodied in this phase. Creativity on the part of the designer is vital in obtaining desirable solutions. The problem of creativity is compounded by the fact that at this stage of the design, every parameter of design may correspond to a fairly large set of options. Structural systems in general are complex and the variations possible in synthesising structural configurations can be quite tedious. Deficient reasoning at this stage results in iterations at later stages of the design process since the basic form of the solution is identified in this phase. In this paper, a design synthesiser is presented, which provides a systematic and structured approach to preliminary design.