The research objective was to draw the ruling criteria for the interior design basics, which associated with the rehabilitation of nineteenth century buildings, by evaluating the basics of the interior design of one of the rehabilitated buildings, the Egyptian Book House. The evaluation based on the results of the analysis of the basics of the interior design of the building spaces through a questionnaire was submitted to a group of architects with experience in the field of interior design and another group with experience of conservation. The majority of the results of the questionnaire indicate that the process of rehabilitation of the building has positively affected the value of the functional building, while the aesthetic and artistic building value affected negatively, the research concludes that all the basics of interior design should be taken into consideration to suit the different building values, whether historical, aesthetic or functional. The main objective of the rehabilitation and adaptive re use process is to preserve the value of these buildings. The research was based on a combined strategy between the case study method and the experiment method, that revealed the points of views of specialists in the rehabilitation of archaeological buildings through a comprehensive questionnaire to maintain and confirm the identity of the building as well as the foundations of interior design and requirements for use , And the most important results of the research is proving an influence of the elements of the interior design on the identity of the historic building.