Typology of method of zoning and determining of building density in city comprehensive plans in I.R.Iran

Iran’s urban planning system has undergone many changes in recent decades. An issue that has had a significant impact on the development of Iranian cities has been that of building density in urban development plans. In order to address the issue, the present article was aimed at specifying the density of residential buildings in comprehensive plans of Iran’s provincial capitals since the preparation of the first plan so far and providing a typology thereof and explaining its features. This original descriptive-analytical article adopted a documentary data collection method with direct reference to access the data, analyzed simply through description of the relationships between them. The findings indicated that five different types of residential building density specification method could be identified: Traditional Method (with three subtypes: Reduction, Incremental, and Three-Level), Floating Method, Strategic-Structural Method, Combined Method, and Other Methods. On that basis, a historical trend was identified in the proposed typology, where each type or subtype in a certain period of the timeline has the greatest impact in specification of the density of residential buildings in cities. Moreover, the study of the historical evolution of such types demonstrated that laws approved by the upper hand and regulations concerning the issue of building density have functioned as turning points for application of these methods in Iran’s comprehensive urban plans. The adoption of the Regulations for Increasing Density and High-Rise Buildings by the Iranian Supreme Council of Architecture and Urban Planning in 1990 turned the inverse relationship between the two variables of parcel size and building density into a direct relationship. This resulted in the development of open spaces and increase in building density in the municipal rules and regulations for construction and urban planning, considered particularly in the theoretical foundations and development patterns in plans. Another important factor in the shift from traditional to three-tier subtypes was the Rules and Regulations for Cities’ Residential Zoning to Apartment Complexes, Multi-households, and Single Units to Preserve Neighborhood Rights in Residential Units, ratified in 1992. Along with the earlier regulations, these induced a lasting change in the approach adopted in the plan to the issue of specifying building density. This approach causes the increase in the density of buildings to be conditioned upon increase in outdoor space, decrease in the level of residential infrastructure, avoidance of segregation, and observance of neighborhood rights through provision of light and sun and avoidance of overlook. Another influential factor that has led to the creation of a strategic-structural type involves the (Comprehensive) Strategic-Structural Plan of the city of Tehran, ratified in 2007, which was followed by nearly all the subsequent plans. Finally, the comprehensive plans of Tehran in 1969, 1991, and 2007 have played an important role in specification of density in other plans, where the widespread zoning of building density began from the comprehensive plan of Tehran ratified in 1969. In general, the study of density specification experiences in provincial capitals can provide urban planners and designers with guidelines for specification of the density of residential buildings. Thus, they can pathologize the existing methods and provide optimal density specification methods based on the requirements of each city and the internal and external advantages, so as to achieve the correct forecast in the use of resources, lands, natural environments, and infrastructures according to population capacity and upper-hand rules.