The BNZ bank says its building on Harbour Quay is to be closed for the next six to eight weeks as work begins to clean up extensive water damage following a strong earthquake on Sunday.
BNZ chief executive Andrew Thorburn said on Wednesday the building's owner has had independent engineers assess it and the bank has also had experts check it.
All the engineers have declared it structurally sound.
Mr Thorburn said the water damage was caused by pipes that burst after ceiling panels dislodged in the 6.5-magnitude quake. Construction specialists are assessing the damage and working out how long it will take to repair.
Staff have been told not to go back into the building, but may be able to retrieve essential personal belongings.
Meanwhile, the Central Library is closed on Wednesday while damage caused by the quake is repaired.
Wellington City Council acting chief executive Derek Fry said inspections revealed small areas of cracked plaster that may fall off in a significant aftershock, but engineers report the structural integrity of the building is not in question.
Mr Fry said the council contractors will remove the loose material and repair the damage. The city's other public libraries would be open.