The badly quake-damaged building on Molesworth St in Wellington will be "deconstructed".
Wellington Mayor Justin Lester told a press conference this afternoon that engineers were still assessing the tower at 61 Molesworth St.
However, he added: "It's likely it will need to be deconstructed.
"Within two hours, we'll know what that plan looks like, we'll know what that process is likely to be."
Lester said there would "not necessarily" be huge disruption as a result.
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Lester said anybody evacuated out of the building on Tennyson street would have accommodation arranged for them if they had nowhere to go.
He said the assessment team initially found 60 buildings "that were of concern to us in terms of showing signs of structural damage".
They then identified about 28 buildings "at the risk of some part of the building ... falling down."
General manager for the building consents team Mike Scott said public safety was "absolutely critical".
The exclusion zone around the building was one and a half times the building's height, which was "international best practice until you have full detail".
Scott said they might be able to reduce the cordon depending on information they received about the building later today.
"We've got to be very cautious about how we do this, we can't put anybody at risk, but we are also critically aware of the impact this is having on the city and that area in particular.
"We're taking a very measured approach but we're doing it at real pace, and make sure that we're going to get things moving as quickly as we can."
Scott said the owner of the building had been "phenomenal" to deal with and had been working closely with them.
He said the owner was "comfortable with the process today".
Lester wanted to thank the engineering community, saying engineers from around the country had been offering their help and were "doing an incredible job".
"Look, we need to be prepared for anything that could happen in Wellington," he said. "We know that we live on a fault line, that's not news to anybody, but we know the biggest risk to anybody is jumping in your car and driving to work."
Scott said Monday's earthquake was the third biggest in 100 years, but Wellington had coped particularly well.
"Wellington has had at best superficial damage across the whole portfolio. It's very little, we have done extremely well.
"We know there are isolated pockets where there have been issues but, as a whole, Wellington has actually done incredibly well for such a significant earthquake. So we're actually really pleased on the whole with the way things have gone."
Lester said the "great news" for Wellington was that investment in infrastructure and resilience had "paid off".
"We haven't had any disruption to water supply, power has remained, which has been a really good outcome ... also sewerage services for the most part."
Having had "rain, earthquakes, severe wind, and then rain again", Wellington had experience "relatively minor disruptions" and the city had "coped phenomenally well".
When asked whether the approaching bad weather for Wellington might put the Molesworth Street building at risk of falling down, Scott said he did not know what weather or aftershocks might do.
"Don't presume that engineering is an exact science. We're in the hand of God with some of these things."
Nobody had gone into the building to assess it as there was such a risk to their safety, he said.