The Living Infrastructure Layer(TM) introduces a new engineering framework that recognizes ecological systems as measurable, permanent infrastructure within the built environment. George Irwin presents nature as a sixth infrastructure layer alongside Structural, Mechanical, Electrical, Plumbing, and Fire Protection systems. Drawing upon more than twenty-five years of international experience, the book explores how living infrastructure can deliver measurable outcomes in stormwater management, energy efficiency, biodiversity, resilience, carbon reduction, public health, and long-term economic value. Written for architects, engineers, landscape architects, developers, municipal officials, contractors, educators, and students, it establishes a practical framework for integrating nature into buildings and cities with the same rigor applied to other engineering disciplines.