Due to the physical, functional and/or economic reasons, historical buildings require interventions while adapting them to the contemporary conditions. Although, national laws based on the international charters and congresses signed also by Turkey have determined the frame of these interventions, the approach of the architect is still one of the basic criteria directing the state of a building after restoration. Thus, together with the interpretation of architect the type of intervention varies.As needed today, interventions, a subject for one of the discussions in conservation, were applied by the past cultures when the consolidation, change in functions and enlargement of spaces was required for the important architectural property belonging to their own culture. Most of these historical buildings, which have to be protected according to the contemporary conditions, contain interventions due to restorations in several periods. These interventions are defined as the qualities to be evaluated and to be protected in the conservation process of the historic building. Thus, the contemporary intervention will also be respected as one of the qualities belonging to one of the periods of the building in later restorations. As the scope of interventions may vary from simple repair to reconstruction, it is necessary to limit the subject. In this study, new exterior additions to historic buildings are focused as major interventions to the historic buildings. What is aimed in this study is to determine the consistency of architectural expression in the preservation of original qualities, before and after interventions according to the principles of conservation. The aim is not to direct the architect for the type of intervention, but to derive the criteria which will form a base in his approach for the conservation of the historic building, through the evaluation of example buildings from İzmir. It is also expected that the evaluation of the examples in İzmir as subjects for several discussions held in the media, will offer a different attitude for these discussions.