Retrofitting is the process of addition of new features to older buildings, heritage structures, bridges, etc. Retrofitting reduces the vulnerability of damage to an existing structure during a near-future seismic activity. Retrofitting a building involves changing its systems or structure after its initial construction and occupation. This work can improve amenities for the building’s occupants and improve the performance of the building.

Strengthening is the process of increasing the load-resistance capacity of a structure or portion. It describes the process of upgrading the structural system of a building in order to improve its performance under existing loads or to increase the strength to carry additional loads.

Rehabilitation is the process of restoring the structure to service level, once it had and now lost, strengthening consists in endowing the structure with a service level, higher than that initially planned by modifying the structure not necessarily damaged structure.