The project has faced controversy since its July 2013 commissioning.
Sanlam Towers will house the firm's headquarters in about three floors.
The development has pushed the boundaries of retail and recreation in Nairobi.
The Beacon will be the biggest shopping mall on the sideline of Nairobi CBD.
Upper Hill is becoming unpopular due to heavy congestion in the area.
The firm has acquired land worth Sh10 billion to facilitate its property development initiatives.
Leakey has obtained Sh300m from Tullow and other oil prospectors in Turkana.
The Sh6.2 billion facility will offer a floor space of 50,000 square metres in three units.
Nairobi's skyline is more crowded due to increased office space supply.
This is the first major revamp by Sarit Centre since its inauguration in 1984.