1 Int. J. Architect. Eng. Urban Plan, 31(1): 1-11 January 2021 DOI: 10.22068/ijaup.iust.2020.101 Research Paper A Critical Investigation of Priorities in Adaptive Reuse Theories within the Interior Architecture of Valuable Buildings: A Comparative Study based on the Nara Document Parameters Seyed Ehsan Masoud 1 , Alireza Einifar 2* 1 PhD. Candidate, School of Architecture and Environmental Design, Iran University of Science and Technology, Tehran, Iran 2 Professor of Architecture, School of Architecture, University of Tehran, Tehran, Iran Received: May 2020, Revised: June 2020, Accepted: June 2020, Publish Online: July 2020 Abstract Changing and repurposing existing buildings for their continued use was quite common in the past and structurally safe buildings were adapted to meet new functions and needs. In modern conservation theory, Adaptive Reuse is an important means of preserving cultural heritage. The main question is what are the priorities and shortcomings of adaptive reuse theoretical references within interior architecture based on comparative study with Nara Document parameters. The research method of this study is qualitative, with logical argument as a strategy. The priorities were studied and then the most important weaknesses and drawbacks of these approaches to Adaptive Reuse were analyzed in a comparative study with the Nara Grid by 32 semi-structured interviews with experts in the fields of Architecture, Interior architecture and conservation. The results show four main Adaptive Reuse priorities extracted from the reviewed literature: Host Space Function, Programmatic Approach to New Use, Technical Requirements and Design-oriented strategies and solutions. These theoretical priorities do not negate each other; in fact, they are rather complementary. However, if one of them gains more importance in the process it can lead to many losses. Of their most important disadvantages, the following are worth mentioning: A physical outlook and a lack of attention to intangible and soft values, a lack of attention to the meaning and characteristics of functions of the building in the past, ignoring the human presence and its needs, ignoring architectural details and interior architecture, lack of interdisciplinary research, and lack of adequate strategies in line with building values. It seems like the issues mentioned above could be avoided and redeemed through an emphasis in conservation policy on fixed feature spaces, semi-fixed feature spaces, and informal spaces in interior spaces, as well as considering human needs and social sciences in the redesign process, and following each priority and approach in the redesign process accordingly. Keywords: Adaptive Reuse, Valuable Buildings, Interior Architecture, Priorities, Nara Grid. 1. INTRODUCTION 1 Changing and repurposing existing buildings for their continued use, has become increasingly important. The demolition and destruction of these buildings is not only harmful to the environment but also harmful to the local identity, cultural heritage and socio-economic values. In the past decades, interventions in existing buildings to preserve and sustain have become a creative challenge in the field of 1 (Powell, 1999; Schittich, 2003). The Adaptive Reuse of valuable buildings has been mentioned Corresponding author: aeinifar@ut.ac.ir * © 2020 Iran University of Science & Technology. All rights reserved in international heritage conservation policy documents and charters as a recommended solution (ICOMOS, 2004; Jessen & Schneider, 2003; J. Jokilehto, 2007; Machado, 1976). Moreover, this type of reuse has been studied in related fields such as urban regeneration, engineering and recycling, sustainability, economics, management … etc. (Bullen & Love, 2010). Other terms such as "Remodeling", "Retrofitting", "Conversion", "Adaptation", "Reworking", "Rehabilitation" and "Refurbishment" have been used in reference to the concept of Ada0259se (Graeme Brooker & Stone, 2004; Giebeler et al., 2009; Habibi & Maghsoudi, 2011; Machado, 1976). Adaptive Reuse is not an emerging phenomenon. In the Renaissance classical buildings were modified for new