Confusion around new guidelines to prevent a building collapse like Statistics House has made owners reluctant to undertake earthquake risk assessments.
Statistics House, built in 2005, sustained damage in the Kaikoura Earthquake that could have killed people.
It prompted the Ministry of Business Innovation and Employment to issue new guidelines for engineering assessments in November 2018.
These guidelines are commonly referred to as the "Yellow Chapter" and sit alongside the rules set in legislation, known as the "Red Book".
The guidelines are based on latest knowledge, but need to be consulted on for a couple of years to determine whether they should become a part of legislation.
That has left the owners of buildings with similar characteristics to Statistics House facing a confusing grey area in the meantime.
They have been weighing up a moral obligation to have their buildings checked against best advice, with the prospect of forking out millions of dollars when there's no legal requirement to do so.
MBIE has commissioned Engineering New Zealand to investigate how the guidelines impact seismic assessments of buildings.
A report into the first phase of that work, called C5 Evidence Project, has been made publicly available.
The report said having both regulations and guidelines in circulation at the same time was adding confusion to an already complex system.
Engineers who were consulted wanted one set of rules representing the most-up-to-date knowledge to refer to when assessing buildings.
But the report also revealed that very few assessments under the Red Book even existed to begin with.
Dual Red Book and Yellow Chapter assessments had to be commissioned for the six buildings used to inform the report in order to actually make a comparison.
The lack of Red Book assessments means many buildings with pre-cast concrete floors have New Building Standard (NBS) ratings based on earlier guidelines that don't consider floor systems at all.
Feedback indicated the Red Book hasn't been used because engineers were waiting for the Yellow Chapter to come out.
"This delay itself increases market uncertainty and decreases public confidence in buildings. It also means any risk a building poses to the public exists over a longer time frame", the report said.
Some engineers have also been advising clients to wait until the Yellow Chapter's regulatory status is confirmed before undertaking assessments of their buildings.
"Building owners want to make the best calls about where to focus investment in their capital assets. This means they want confidence that retrofit work is be aligned with any imminent regulatory environment."
Meanwhile businesses and Government agencies vacating buildings has contributed to confusion around seismic assessment regulation.
"Some building owners are setting a precedent for building scrutiny, closures or departures over and above what is required in current regulation", the report said.
The most prominent building to be vacated is Wellington's central library through which pre-cast concrete floors are used extensively.
The guidelines cannot be used to determine an NBS rating because they are not the official rules yet, but engineers calculated that hypothetically the library's would drop dramatically from 60 to 15 per cent.
Anything under 34 per cent NBS is considered earthquake-prone.
The report said business owners were acutely aware of health and safety risks.
"This means they are concerned to make all reasonable efforts to safeguard staff and other people from any perceived risks presented by buildings."
Some owners of buildings with pre-cast concrete floors are worried their NBS ratings will face a similar fate to that of Wellington's central library when tested under the Yellow Chapter.
The report found there wasn't a substantial difference in NBS ratings between the Red Book and Yellow chapter. Only the six buildings assessed, two went up and one went down.
But if their current building assessment is based off earlier 2006 guidelines, it wouldn't make a difference whether it was the Red Book or the Yellow Chapter their building was measured against, the NBS ratings would decrease regardless.
The Red Book and Yellow Chapter did however identify different vulnerabilities in buildings, which means any remediation using the current rules might not address the biggest weaknesses.
MBIE building systems and performance general manager John Sneyd said during consultation the ministry has received questions from building owners and engineers asking whether it's mandatory to use the Yellow Chapter when assessing buildings.
"MBIE has worked closely with Engineering NZ and other groups, such as the Government Property Group, to provide clarity, he said.
"MBIE will consider any regulatory implications of Engineering New Zealand's findings once they are complete."
An Engineering New Zealand spokeswoman said they have always provided clear advice to engineers about which rules and guidelines to use and when.
She confirmed they were in the second phase of collecting evidence for MBIE to help inform the ministry's future decision-making.