Public housing represents a notable percentage of the housing stock in many developing countries. Its shortcomings have been identified and examined by many scholars and experts in an attempt to investigate the possibilities of improvements in future projects. Yet, for many years and through their own initiative, dwellers in public housing have been engaged in alteration and extension activities aimed at adapting their dwellings to better suit their needs. These activities have resulted in the transformation of entire housing developments in many parts of the world. Understanding this phenomenon is a prerequisite to any attempt to provide better quality housing environments and to improve living conditions in existing ones. Therefore, this paper examines the development of transformations in different public housing projects in Egypt. A wide array of transformations were recorded during a survey of twenty projects in Cairo and Alexandria, from which it was possible to establish a typology of transformations, to examine the use of building materials and resources, and to distinguish between different patterns through which transformation activities take place. The study identifies some of the implicit factors that control change at both dwelling and community levels. It was found that user transformation of public housing projects should not be considered as a simple space enlargement process, but rather as a result of a complex set of inter-related determinants associated with both context and dwelling characteristics.