What process involves the addition of portions to existing buildings?

The process that involves adding portions to existing buildings is known as the extension of buildings. This is a specific type of construction activity that focuses on physically expanding an already existing structure by introducing new spaces or areas.

Extensions can take many forms, such as adding additional floors, rooms, or features to facilitate more functional use of the space. This approach maintains the integrity of the existing structure while enhancing its capacity or usability, effectively allowing for growth or adaptation to changing needs.

In contrast, options like basic renovation typically involve updates or improvements to the current elements within a building, such as finishes, fixtures, or systems, but do not add to the building's footprint. Complete reconstruction would imply that the building is being entirely rebuilt from the ground up, which does not involve merely adding onto what is already there. Demolition and rebuild mean completely clearing the existing structure and constructing a new one, which again differs from simply extending an existing building.