Although the original spatial organization of a building is always established by its first architect, subsequent interventions on the interior did not they will maintain that scheme, and for obvious reasons, older structures are often modified by designers of a different generation according to the changing needs of society, as well as the evolution of the city.

This process often re-semanticizes the building as a consequence, and is based on the idea that buildings are never completed and neither they are unalterable.

The interior architect must be sensitive not only to the place of the building in its physical and socio-political context, but to the temporary needs of change of owners and users. In this sense, if the building has “good bones” the original architectural idea, therefore, is the first thing to consider in a new spatial organization, the rest will subsequently be obliged to follow it.

There are many different degrees of alteration – minor to enable a building and meet the new standards and regulations, it is likely an extension of the first interior space (or even of spaces created later), or major alterations, such as the total modification of a building including the facade, which will cause the effect of a new building. All possibilities between these two extremes are within the domain of the interior architect.

If the practice of architecture has to do with the art and science of a new building, then the practice of interior architecture deals with the renovation of existing buildings to make way for new uses.