Genetic changes are understood as these, that have existed throughout history in the primal pattern, so it will concern the change of threads of construction technologies, construction function and materials used. generally, this classification enters into ideological assumptions, and not the static-strength values. In this regard, the following three groups of systems can be distinguished:
1. Masonry systems or historic complexes that have not been transformed, which are characterized by an original technological and compositional structure for a given period, contain authentic materials, at the same time, they retain their original functional and utility purpose and have a proper shape of the construction form.
2. Systems or complexes previously transformed congenially, whose technological and structural structure, both in terms of form and function, it retains partially or mostly all the features corresponding to a given historical period, but it doesn't really belong to this period, being a new substance faithfully reproduced in a similar or analogous material (np. reconstructed or restituted objects or complexes).
In this case, the historic value of the system is determined by the percentage ratio of old and new substances. It is the higher the more authentic parts there are and it decreases as the predominance of new parts over the original parts increases.
3. Masonry systems or rebuilt units, characterized by this, that technological construction, form and decor or utilitarian and structural purpose have been transformed to such an extent, that the original features of historical authenticity have been completely distorted and lost.
In this case, from the historical and scientific point of view, the age criterion remains in the assessment of the building, in which these changes were made, and sometimes emotional, decorative or social.