The art of designing additions carries with it a host of unique challenges. Especially, in the case of annexes and extensions in historical buildings, ideology can be an important factor in shaping the design of the addition. Ideology.s close relation with the concept of identity also makes it a factor in shaping additions in historic buildings. However, studies about the subject generally address themselves to the examination of the functional necessities, and aesthetic concerns. Additions in historic buildings are mostly evaluated within the scope of conservation, and with their harmony to the historical context. This study attempts to analyse the design of additions in historical buildings from a different perspective, leaving aside the principles conservation and discussions of contextualism. The aim of the thesis is to analyse the reflections of ideological and social changes in the physical environment, and to examine the additions in historic buildings from that point of view. Within the scope of this thesis additions in historical buildings are investigated with special emphasis given to the concept of ideology. The interaction between ideology and architecture is explained through an examination of international and local samples. Also, the concept of conservation and historic building is discussed in relation to ideology. Basic reasons for building new architecture in historic settings are examined. Finally, classifications of addition buildings according to their location design approaches, and combined expressions are made.