New information on hollow core floors suggests they could pancake in a strong earthquake.
Wellington could be particularly hit with the problem, with over 120 buildings containing the flooring. The central library indefinitely closed last month due to the risk.
TVN1's Q+A was contacted by professional engineers who claimed office workers around New Zealand were unaware of the potential hazard and were concerned this had not been addressed seriously by Government.
Hollow core floors consist of pre-made slabs of concrete lifted onto seating along a beam, then covered with reinforced concrete.
During the 2016 Kaikoura earthquake, pre-cast floor slabs slipped off their seating, causing the partial collapse of the Statistics NZ building. As a result, expert engineers began to look at the pre-cast flooring, giving special attention to the hollow core.
After Kaikoura, seismic engineers collated the latest information about pre-cast floors and recommended changes to building assessments.
As a result, late last year the Ministry of Building, Innovation and Employment (MBIE) published new voluntary assessment guidelines.
In Wellington, the city council assessed the central library building under these new guidelines, and Wellingtonians were told their library was closing indefinitely that same night.
Mayor Justin Lester said the assessment suggested "we could have floors collapsing and pancaking and potentially people dying".
"That is not a situation we are happy with."
The assessment found the library’s hollow core floor slabs could move off their seating in a large earthquake with very little sway.
Engineers emphasise not all hollow core or pre-cast floors are a high risk and the building could have other redeeming features.
MBIE said it would spend two years doing an impact assessment before deciding whether to make the assessment mandatory.
National MP Andrew Bayley said this time frame was "outrageous".
"Not only are property owners confused, but people working in those buildings don't know whether they're safe."
MBIE declined to be interviewed by Q+A, but said although the guidelines are voluntary, responsible and vigilant building owners may choose to use the proposed revisions.
When asked about voluntary guidelines around pre-cast flooring, Minister of Building and Construction Jenny Salesa said: "There is the red book versus the yellow book the way MBIE is looking at things".
She said she was seeking further advice from MBIE on the issue.
“I am working on it pretty urgently… I am looking at the whole Building Act 2004 as we speak.”