This study sets out to investigate the transformation of house types in relation to changes of urban built forms. From the title it is clear that this study includes two major arguments. One concerns housing transformation where the focal point is change. The other is typo-morphology, which concerns the approach of the study to that change and the issues of type, typology and morphology. The study looks at long term processes of change in housing types in Tehran in chronological order to see how new house types are introduced or designed and built and how traditional types have been transformed to become modern: why, how and by what means they evolve and adapt to new needs and different circumstances. It addresses the transformation of house types, as one dominant type of dwelling replaces another. Of course there are cultural factors at work here, and the influences of architectural fashion. But there are also questions of increases in density, rising land prices, the impact of growing car ownership, planning policy and legislation. Ultimately this study tries to answer a core question: Was there something necessary about the evolutionary process of housing in Tehran or given the present block sizes in Tehran, could there be anything different from the current norms for built forms? Using morphological analysis, more specifically plan analysis, the relationship between type of house and built form of the fabric is explored and examined. The analysis is carried out at residential level and at the scale of buildings, plots and blocks. The emphasis is on the built forms and external envelopes of houses, more than the details of internal planning. The particular focus of this study is the relationship of plot size and shape with house type and the various ways of aggregating plots to create different urban built forms. The analysis is focused therefore on questions of plot size and shape; pedestrian and vehicular access; natural lighting; and the provision of open space around dwellings. The relationship between type of house and built form is explored and examined using morphological analysis and by reference to the ‘archetypal building’ proposed by Steadman (2001). The sample areas are selected from three boroughs of Tehran corresponding to important periods in its morphological transformation. The analysis tries to bridge between three main themes shaping three chapters: planning, geography and architecture (typo-morphology). Three phases of analysis are conducted at different scales. The first phase is the impact of planning and legislation. The second phase is the analysis of plot size and built form, first at the macro-scale of the three selected representative boroughs and then in smaller areas within those boroughs for a more micro-scale analysis. The third phase is the abstract analysis, which is the enumeration of geometrical/configurational possibilities by sketching out the theoretical possibilities that plots could have. There then follows a comparison of these with the actual plans observed in different areas. The study seeks to provide data and develop an understanding of the influences of plot shape and dimension in different parts of the city. It helps to understand the patterns of distribution of different plots and house types in different periods of the city’s expansion. Finally, comparing and synthesizing the results of analyses indicates other actual examples and scenarios that could have happened, thereby showing how houses in Tehran could have changed differently in other directions, and the fact that that is still a possibility.