This thesis extends current adaptation theory by considering the practical realities of adaptation and demolition decisions at the masterplan scale. As existing adaptation theory mainly focuses on individual buildings or the city level, it is not sufficient for explaining decisions on large brownfield sites being redeveloped through the implementation of a masterplan.

A qualitative inductive approach was used to generate new knowledge about the topic. Initially, data was gathered from interviews and focus groups with built environment professionals. In-depth case study investigations of masterplan developments containing former industrial areas were then undertaken. The locations were Cambridge, UK; Eindhoven, Netherlands; and Sydney, Australia. Examining decisions in these different contexts unpacked the realities of how and why adaptation decisions on masterplan sites are made in practice.

For individual buildings, existing literature argues that the physical attributes of a building are the major factor in decisions to adapt or demolish, due to their impact on construction costs. At the masterplan scale, these factors are still applicable. However, the primary data analysis shows there is a different interpretation of economic viability as costs can be offset elsewhere within large developments, and that there are a number of additional issues considered at the masterplan scale. These include the relative scale of buildings and considerations of vehicle and pedestrian flow through the site.

There are two benefits of building retention which are commonly cited in the academic literature: conservation of heritage and savings in materials, and therefore savings in embodied energy and greenhouse gas emissions. In practice, the role of heritage was found to be frequently considered at an individual building level and in some instances is thought out at a larger physical scale, notably as part of place-making within a masterplan. However, embodied impacts were found to be rarely considered in adaptation decisions at either the individual building or masterplan scales. This difference, it is suggested, may be due to the fact that heritage has been included within planning policy for many years, while embodied impacts are only just starting to be included. The three case studies uncovered factors that govern decisions on large urban developments. People involved in, or affected by, masterplan developments including planning authorities, local communities and individuals were found to have a significant influence over the decision-making process, which is also contingent on the structure of the planning system and economic conditions at the time decisions are made. Due to the long time-span of masterplan developments, these decisions may also change at a later date in the development process.

The theoretical underpinnings of urban development including equilibrium, structural, event-sequence and agency models, are applied to the research findings to offer a potential theoretical framing applicable to the masterplan scale. Through the multiple lenses provided by composite models, the variations in the factors governing decisions are explained. These include the influence of hierarchies within the planning system, the ability of developers to negotiate with local authorities over planning policy requirements and the transfer of risk to individuals willing to take it. Through the exploration of these complexities which are exacerbated by the physical and chronological scale of the masterplan, current adaptation theory is extended and practical recommendations made.