A review of design models for behaviour change established that although design with an intent to change human behaviour is a topic under discussion, there is a need to understand better the perceptions that professional spatial designers hold on human behaviour and how to influence it. Therefore this thesis aimed to identify designer’s perceptions on what can change human behaviour [RQ1], to isolate what may inform their perceptions [RQ2], and to establish in what ways these perceptions compare with existing human behaviour theory [RQ3]. Multifaceted interviews were conducted with spatial designers who self-identified as practising in Design for Behaviour Change [DfBC]. Within method triangulation and thematic analysis identified nineteen distinct experiential concepts which indicate how designers think that user-occupants might experience intentional design. These concepts have been connected to human behaviour theory to identify some theories that can inform design for behaviour change. In addition the analysis identified four mitigating factors and five perception determinants that inform real world design strategies for behaviour change. Synthesis of these findings represents an entirely different way of thinking about the phenomenon of DfBC in that it separates “what” (the experiential concept) from “why” (human behaviour theory) to make sense of it. Coupling an experiential concept with an applicable human behaviour theory creates a behavioural lever that better targets specific behaviour. Some of the theories can influence more than one behaviour factor depending upon the experiential concept that is applied in the design. It is the behavioural levers (the combination of an experiential concept with a human behaviour theory) that creates a more complete understanding of DfBC. The results are diagrammed in a framework for designers and researchers to use.