Protective structures are built to provide long term protection for the immovable cultural heritage against the possible damage that may arise from environmental conditions such as rain, wind and sun as well as the activities of the living like vegetation and uninvited animals. Most of the protective structures have been found to be inadequate to fulfill this purpose and conservation problems were observed on the remains under those structures. The inadequacies are mostly related to the architectural design of the protective structures. The aim of this study is to identify the architectural characteristics which have an impact on protective efficiency and how they are related to the deterioration factors. With this scope, sixteen protective structures that were selected from Turkey and abroad were analyzed through site surveys and literature studies. In order to identify and assess the role of protective structures on creating deterioration factors, this study groups the design characteristics under typology, structural system, roof system, roof material, façade system, façade material, thermal control system and drainage system and the deterioration factors under sources of water, instability of microclimate and the activities of the living. The relationship between these groups were analyzed and evaluated. As a result, the type of the protective structure as a shelter or an enclosure, selection of the design elements such as roof and façade systems as well as the materials, proper application of thermal control systems and drainage systems are the main characteristics of the design that determine the efficiency of the protective structures. The study will make important contributions to the theoretical and practical aspects of the design process of protective structures.