Ministers warned against confusing ‘indefensible’ engineering guidelines in major earthquake

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Many buildings in Wellington had to be demolished in the aftermath of the Kaikoura earthquake. Photo/Mark Mitchell

Ministers warned that confusion over engineering guidelines issued after the partial collapse of the Statistics House would be inexcusable in the event of a major earthquake.

The Statistics House, built in 2005, was damaged in the Kaikoura earthquake that could have killed people.

The Department of Business, Innovation and Employment (MBIE) pushed for new guidelines for engineering assessments in November 2018.

The guidelines are commonly referred to as the “yellow chapter” and sit alongside the rules set forth in the legislation, known as the “red book”.

The MBIE is still deciding whether the yellow chapter should become part of the legislation.

So although the guidelines are based on the latest engineering knowledge, they cannot be used to determine if a building is vulnerable to earthquakes.

This situation has left owners of Census House-like buildings in the meantime facing a confusing gray area.

They have to balance the ethical obligation to inspect their buildings against the best advice, with the potential to pay millions of dollars when there is no legal requirement to do so.

The Statistics House has now been demolished. Photo/Mark Mitchell

Wellington City Council officials and Mayor Andy Foster raised the issue in a meeting with Housing Secretary Megan Woods and Building and Construction Minister Botto Williams in May.

In a ministerial briefing memorandum obtained by the Herald under the Local Government Official Meetings and Information Act, the council sought to clarify the relevant applications of the Red Book and the Yellow Chapter.

“We are concerned that confusion over this issue would not be warranted if we had a major seismic event,” the note said.

The engineering advice was a step in the right direction, but the policy remained unclear, said Mike Mendonca, city council’s chief resilience officer.

“The council is keen to see clarity on this issue, and we would like to see it resolved only after an earthquake,” he added.

Wellington City Council has already made important decisions based on the guidelines. The Central Library closed after the building was evaluated according to the guidelines.

The library was given a theoretical rating of the new building standard of just 15 percent – a significant difference from its technical rating of 60 percent.

Minister of Construction Bhutto Williams. Photo/Mark Mitchell

Williams said she took public safety issues very seriously.

“Our knowledge of structural engineering evolves over time. It is important to be careful when making decisions about when and how to reflect new knowledge into the building regulatory system.”

Williams said the decision on incorporating the yellow chapter into the legislation rests with MBIE and she supports the department’s careful examination of the issue.

MBIE considerations have been going on for nearly three years now.

As part of its consultations, MBIE commissioned two reports from Engineering New Zealand to investigate how the guidelines affect seismic assessments of buildings.

They found confusion and uncertainty in the market and owners’ reluctance to conduct earthquake risk assessments until there was clarity on the regulatory status of the yellow chapter.

This reluctance has resulted in many buildings not even being evaluated under the Red Book, which means that buildings with precast concrete floors have NBS ratings based on previous guidelines that do not take into account flooring regulations at all.

Mike Mendonca, Wellington City Council’s Chief Resilience Officer. The attached photo

But the reports generally found that there was no significant difference in the NBS ratings between the Red Book and the Yellow Chapter.

However, it was found that the yellow chapter provides better insight into building weaknesses, which means that it better targets the parts that need strengthening.

Jenny Tippler, MBIE’s Director of Building Performance and Engineering, said MBIE needs to consider the findings in the latest report before making a decision on the legislative framework.

“MBIE is committed to ensuring that building legislation operates to protect the health and safety of people and buildings. Engineering knowledge is constantly evolving and MBIE will always balance this with the need to provide certainty to the sector.

“Building owners must have the certainty that, after they comply with the mandatory national requirements, the level of compliance will not change in the short term.”

Tippler reiterated that the yellow chapter cannot be used to determine if a building is earthquake-prone under the building code.

“However, engineers may continue to use additional technical information, including the yellow chapter, to complete engineering assessments for other purposes and to support discussions with building owners about such matters as repair options.”

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