Abstract: A modular system of construction of loft apartment buildings. This type of unit is in high demand in many metropolitan areas, and the modular nature of the inventive buildings allows them to be produced quickly and at low cost. In addition, the invention provides a novel system for interconnecting apartments quickly during construction, providing further cost savings. A mix of apartment types, including handicapped-accessible apartments, may be placed in each building, with the proportions of different apartment types being tailored to the needs of the local market and the constraints of local building codes. The apartment modules may be sized to permit convenient shipping of modules within the constraints of overland shipping regulations.