Since the first publication of this book on multi-story pneumatic and fluid-inflated building structures in 2013 the author has continued research into extensions of the same principles to large span floors and roofs. Whereas the initial focus was on lightweight vertical structures such as air-supported multi-story buildings with flexible plastic membrane enclosures and pressurized thin-walled columns with rigid metal walls, the new research has centered on lightweight horizontal structures. This book is about a very different kind of architecture than the buildings we see around us at the beginning of the 21st Century. It explores the use of air and liquid pressure as the principal structural element of multi-story buildings. The internal fluid pressure greatly increases structural efficiency by converting columns, floors and roofs into lightweight tension structures. Several variants of such building structures are examined in detail. In multi-story air-supported buildings the internal building environment is maintained at a pressure that normally does not exceed twice atmospheric pressure, so that the physiological impact of a hyperbaric environment are minimized. The entire building acts as a column with a circular cross-section and a lightweight flexible membrane wall that is surrounded by a network of diagonal and horizontal cables. Floors are suspended from the roof, which is directly supported by the ambient internal air pressure. The structural design, fire protection, water and sanitary services implications, airlock entrance and exit facilities, thermal characteristics, construction sequence, comparison with orthodox building costs, and general safety considerations are discussed. A prototype multi-story air-supported building constructed as a student project by the author at the University of New South Wales in Sydney, Australia is described in detail. A less revolutionary structural alternative consists of one or more columns that are internally pressurized with water, air, or a granular material. Typically composed of a thin metal wall such thin-walled cylindrical shell structures (i.e., monocoque cylinders) have received a great deal of attention from mechanical and aeronautical engineers due to their wide-spread application in aircraft, missiles, and rockets for space travel. The application of such pressurized columns in multi-story building structures is examined both from the point of view of providing vertical support for suspended floor systems, as well as serving as the horizontal compression counterpart of suspension cables in lightweight floor systems. A prototype building supported by an internally pressurized central column that acts not only as the vertical support element but also as a store for solar heat collected at roof level is described. In this 2nd Edition an entire chapter has been added on air-supported and fluid-inflated horizontal structures suitable for building floors and roofs. In these structural systems internal fluid pressure counteracts the forces exerted by cables that support the building occupancy loads. Large span floors in excess of 200 feet are feasible with a self-weight of less than 20 pounds per square foot of floor area. Chapter 7, which previously included an introductory section on pneumatic cable floors, has been divided into two chapters. Chapter 7 now deals exclusively with vertical rigid membrane air-supported and fluid-inflated building structures. The previous Section 7.6 dealing with pneumatic cable floor systems has been expanded into Chapter 8. Due to the comprehensiveness of new research Chapter 8 has grown in size beyond Chapter 7. The book also includes a comprehensive historical review, structural design analysis, behavior under wind loads, examination of thermal characteristics, and material requirements of single-story air-buildings in two appendices. Such buildings have been in common use for mostly large-span applications since the 1940s.