This thesis advances a proposition that designers of exemplary industrial buildings adopt design heuristics based on evolving conceptual prototypes. The detail design priorities and formal expressions may vary, but the essential structure of their design solution search patterns should show a high degree of commonality. This commonality is based on the balance between rational and intuitive strategies for design decision making. Therefore it is the central objective of this thesis to demonstrate that a pattern between these two cognitive approaches to design thinking occurs across the cases investigated. The research was organised as a comparative study of the design process used by a selection of designers to design industrial buildings which subsequently received design awards for the quality of their design. Through a series of six case studies using semi-structured interviews and follow-up repertory grid analysis, data was obtained which allowed the various design methods to be recorded, analysed and compared. A control sample of designers of non award winning industrial buildings was also conducted as a comparison to validate the classification of designers on the basis of design quality on the grounds of design awards. The thesis will propose that each designer resorted to a constantly evolving genenc 'prototype' for the design of industrial buildings which helps reduce the search area for a design solution. Therefore relatively little time is required to analyse the problem at the beginning of the process before a suitable solution is formulated. The prototype allows the designers to quickly identify aspects of the design that might prove problematic and hence require specific attention. The strategy is then one of rational analysis to solve specific problems rather than an extensive rationally based development of the whole design. Hence the supporting role of rationally based techniques during the design process. Finally, the familiarity that comes from using a design method based on a constantly evolving prototype provides the designer with greater 'outcome certainty', in that they have an increased likelihood of achieving a successful design as the potential of the prototype is known to the designer at the commencement of the project