Intrigued by the parallels he saw between patterns of growth in nature and vernacular architectures, Jørn Utzon developed a succession of projects based on open-ended building systems. Christened 'Additive Architecture' in the office in Sydney, these ranged from the timber 'Espansiva' housing to a majestic precast concrete stadium complex in Saudi Arabia. In the first part of this book Utzon's principal assistant Mogens Prip-Buus - who proposed the term 'additive' - introduces and presents a comprehensive documentation of a fascinating body of work that acquires new relevance in the age of digital production. This is followed by Utzon's final thoughts on the additive principle, discussed in an extended interview with the publisher Torsten Bløndal, and a selection of superb photographs of the natural environments and buildings and settlements from which Utzon drew inspiration.