It is becoming increasingly clear that there is a gap between the ex- pected and actual performance of buildings. A growing body of evidence sug- gests that the most common barrier to achieving design intent is the absence of comprehensive information during design and construction stages, leading to poor decision-making which impacts on performance and Whole Life Cost (WLC). Building Information Modelling (BIM) has the potential to facilitate a more comprehensive and accurate design approach from the early stages. A de- tailed and accurate model can allow designers and clients to understand the wider impacts of design changes, and to track this information through con- struction stages. However, dependencies between design decisions and WLC have yet to be understood. This paper is based on a project that focuses on the Private Rental Sector (PRS), which is the fastest growing new sector in the UK housing market, also known as Build-to-Rent (BTR). The study adopts a mixed method approach for the development and validation of a structured standard- ised process for more accurate WLC estimation through BIM. As a result, the main problems in WLC BIM management are identified, and coordinated into a reverse-engineered systematic process that uses the Integrated DEFinition (IDEF) 3 structured diagramming modelling technique, and the Industry Foundation Classes (IFC) as a basis for large dataset management. The research out- puts aim to enhance BIM lifecycle management through a smart decision- making approach that is integral to the natural design development process.