Architects rely heavily on adapting/imitating types, precedents and generic solutions to the situations they face. This chapter provides a structure for the discussion of building and urban design types of importance in architecture today. It stresses the need to understand how specific ideal types function before imitating them. The chapter ends with a cautionary case study of the application of a standard housing model to three mass housing projects in Philadelphia. The three were designed by major architects (Louis Khan, Oscar Stonorov, and I. M. Pei). Two have been demolished. They were not designed with the needs of their inhabitants in mind. The other was. Policymakers and architects did not understand the needs of the former; they did of the latter. There is nothing inherently wrong with any building type. Its affordances need to be understood within different cultural frames.