In the UK, healthcare built environment design is guided by a series of long established design standards and guidance issued by the Department of Health. More recently, healthcare design focus has broadened to encompass new approaches, supported by large bodies of credible research evidence. It is therefore timely to rethink how healthcare design standards and guidance should be best expressed to suit ‘designerly ways’ of using evidence, to improve their use and effectiveness in practice. This research explored how designers use performance and prescriptive approaches during the healthcare design process. Three in-depth healthcare built environment case studies were used to explore how designers employed such approaches during the design of selected exemplar design elements. Results show that design elements in the pre and conceptual design phases significantly employed performance based approaches, and due to project-unique circumstances, prescriptive solutions were often significantly modified based on performance criteria. For design elements in the detailed and technical design phases, there was significant use of solutions based on prescriptive approaches, whilst performance-based criteria were used to evaluate design solutions. This research proposes a performance-based, specification driven healthcare design with supplementary prescriptive specifications provided for optimum healthcare environment design.