While cheaper mass-customisation technologies are becoming available, architectural design strives for ever more complex and less regular forms. The increasing costs associated with this tendency are difficult to control. Key factors contributing to this cost increase are non-uniform building components. Focusing on space frame construction, this paper examines the possibility of creating apparently irregular structures from relatively small sets of identical parts. Starting with an examination of the cost implications of irregular truss construction, a case study of the Beijing National Swim Center's space frame system and the conflicting natures of bottom-up and top-down generative logic in this context is presented. The paper concludes with the description of the development of a truss system that incorporates various design variables that increase visual irregularity. Learning from the past, this new system draws its basic logic from classic space frame principles but applies present-day computational logic to achieve new aesthetic effects and structural possibilities.