The paper describes a prototype design system based on genetic algorithm to evolve concept designs, which are coded in an action grammar. The action grammar captures the design intents expressed by the designers’ strokes during sketching process. The model is based on the assumption that the strokes made by the designers embody the aesthetic intentions expressed through the product form. The knowledge about the design generation is captured and used by the artificial neural network and genetic algorithms respectively. Principal component analysis s is used for the tacit knowledge extraction in the form of heuristics. The proposed formalism is able to support the design within a family as well creative design. The model shows the promise of a conceptual design support system for the exploration of the form during early stages of the design.