Tenants in the earthquake prone building in central Wellington have been told they won't be allowed back for at least six months.
About 700 people were evacuated from the Boulcott Street office block two weeks ago after an engineer concluded that cracks in the building were more severe than originally thought.
The property manager and building owner have decided to strengthen the building while it's vacant and have encouraged tenants to find other office space.
In an email obtained by RNZ tenants were told "early indications show a minimum of six months is likely required to complete the work. For the purposes of finding alternate temporary accommodation, we suggest you endeavor to find space for a minimum of 6 months with renewal options to extend this out i.e. further 2 x 3 months."
The scope of the work had been drafted and would be finalised in the near future - the work would involve the installation of steel collars around the building's middle columns and filling the cracks in the floor slabs, the email to tenants from Property Manager Melissa McGhie said.
Jacqui Haste from the City Council said they haven't ruled out re-assessing other buildings in the CBD.
"So council has met and discussed what this might mean for other buildings around Wellington and the wider implications and at this stage we're going to get some independent engineering advice and based on that we'll make a decision."
This was an isolated case, she said.