Coevolution of urban form and built form: a new typomorphological model for Tehran

The paper brings analytical and typological models to the study of the coevolution of urban form and built form in Tehran. It follows the transformation of housing at both urban and architectural scales. At the urban scale, residential areas in Tehran have evolved from small irregular blocks to larger regular grids. At the architectural scale, residential units have evolved from courtyard houses, to terraced houses with south-facing courts, to multistorey apartment units. How do these two processes of evolution relate to each other? Are they entangled in a coevolutionary pattern, or do they remain independent evolutionary developments circumstantially brought together? The paper answers this question by looking at a series of stereotypical built forms for housing in Tehran over time, and by developing a model that brings together parameters of urban structure including block and plot size, and ground coverage ratio, with parameters of built form including access frontage, day-lit depth, and plan shape. In order to build the model and quantify its parameters, three areas of Tehran, representative of its three key stages of growth, are analysed using GIS. The model is found to be capable of approximating reality. During a process of design experiments with blocks of the same dimensions, it is found that alternative built forms are possible, all conforming to similar ratios of ground coverage, floor space index, day lighting, and road access.