A Framework for Determining Visual Buffer Zones AroundUrban Heritage BuildingsCase Study: Alaoddoleh Tomb-Tower, Moayyerolmamalek Mousqeand School & Zand Houses

As a result of an irregular urban renewal process, numerous new buildings which are often incompatible with the visual elements and qualities of their contexts, have been constructed in old parts of cities where valuable historic buildings are usually located. These constructions cause damage to the visual integrity and relation between the historic buildings and their context, and also harm or block the views towards them, reducing the opportunity for the viewer to recognize and appreciate aesthetic and cultural values of the buildings. Determining visual buffer zones for the historic buildings and implementing related regulations to their sourounding areas, which control the visual dimensions of new buildings, are considered a useful tool for mitigating the negative impacts and restoring the visual qualities mentioned. This paper aims to develop a framework for determining the visual buffer zones and the related regulations, which suggests the essential visual parameters that must be considered, and the main structure of necessary guidelines that must be implemented. The literature review is conducted on key concepts of the research such as definition and a brief history of implementation of buffer zones for heritage properties, different aspects of visual dimensions of built environments, and the main visual qualities of urban spaces. On this basis, the theoretical framework is developed which represents the definition of and the approach towards the visual buffer zones for urban heritage buildings that is adopted in the reaserch. To achieve the research objective, a descriptive-analytical study is carried out on three urban heritage buildings, which their visual conditions are affected by inappropriate new buildings constructed in their proximity. In the first stage, the visual characteristics of each historic building and its context are investigated. Secondly, the visual dimension of all kinds of existing human prospects towards the historic buildings, including linear and wide views is analyzed as a whole to indicate the main visual parameters responsible for the visiual situation of the prospects. Mosque and religious school of Moayyerolmamalek in Tehran, Alaoddoleh Tomb-Tower in Varamin and Zand’s houses in Qom, have been selected as the case studies, by considering a number of factors such as the diversity of use and architectural typology. The data is gathered by taking photographs of each historic building from the existing views towards them, desk research, and other relative methods and analyzed mainly through image processing, using graphic softwares. Based on the results,  main visual parameters which must be considered in determining appropriate visual buffer zones are recognized and classified in two groups: the “context parameters” such as location, topographic conditions and massing of the buildings forming the context, and the “historic building parameters” such as height, scale, materials and details. Additionally, based on analyzing and comparing the parameters’ scale of impact, the structure of essential visual guidelines is suggested as a spectrum including fundamental to secondary guidelines in three main classes of “height”, “massing” and “façade composition and details”.