The publication is an attempt to study legal patterns on the example of the integrated object of reality in the German legal system. The sources analyzed are the late 19^th century civil code, later German legislative acts including the Condominium Act of 1951 (Wohnungseigentumsgesetz) and the works of experts in civil law. The article studies the major theories of the concept immovable property, analyzes the legal association between land plots and buildings on them making up res communis – a single economic unit (object) having originated in Roman law . The author describes and reveals the legal difference between mechanical, space and functional integration of things. The article studies the regulation of such concepts in German law as a construction of a single economic unit and its purpose, its essential and illusory components. The paper provides the criteria of a building and material essential component of a single economic unit under German law, shows the specifics of the independent property status of the single object illusory components and the influence of the French Civil Code on German law, studies general and particular aspects of the institution of housing property in modern Germany. Attention has been paid to the issues caused by the unification of the legal regulation of property relations between Western and Eastern Germany when the GDR joined the FRG. The issues were caused by the fact that the GDR legal system had the concepts of the right of ownership and disposal whereas FRG law prioritized the institution of property and associated rights and obligations.