‘Have we gone overboard?’: Quake-safety architects call for rethink

Monday, 20 November 2023

Michael Fowler Centre recently had a quake-prone notice issued.

Key architects of standards that saw Wellington’s Opera House and Michael Fowler Centre added to the capital’s 572-long list of quake-prone buildings say we may have gone overboard.

At the root of the issue is the new building standard (NBS). If a building is deemed below 34% of NBS it is labelled quake-prone and owners are given a time frame to fix or have the building condemned.

Hutt Valley developer Kevin Melville had one building checked by three engineers in the same period. One said the building was 50% of NBS, one said 7%, and the third one was halfway between.

Wellington’s ‘quake-prone’ Michael Fowler Centre is neighbours with the City to Sea Bridge, which may be too-costly to fix, and the Town Hall, where strengthening costs have blown out from $43 million to up to $329m.

The earthquake-prone building register has 572 quake-prone Wellington buildings including the Wellington City Council-owned Town Hall, where works to strengthen it have blown out from $43 million to up to $329m. The nearby City to Sea bridge, not on the register , is said to need strengthening but may be demolished as the cash-strapped council, which recently had the Michael Fowler Centre and Opera House added to its growing fix-t list, looks to save money.

David Hopkins is one of the main architects of the NBS percentage system but said changes had taken away a crucial component. Before 2017, an engineer could use their expertise to say if the building was safe regardless of the NBS rating.

This was no longer the case, and a rating below 34% meant an automatic quake-prone listing.

An otherwise-safe building that had just one component, such as a stairwell that fell below 34%, could be deemed quake-prone in it entirety.

“The settings need to be reviewed across the board. Have we got the settings right or have we gone overboard?,” Hopkins said.

Wellington’s Opera House was also recently added to the quake-prone list.

Holmes Group chief executive John Hare, a member of the New Zealand Society on Earthquake Engineering who helped on the 2017 changes, said the issue had “developed a bit of a life of its own”.

The 34% limit was a hard standard that meant work was needed to strengthen buildings but the risk of someone getting killed in the building was often low.

“It’s a fairly blunt tool. It’s not intended to get down to fine detail. It’s being used for reasons it wasn’t meant to,” Hare said.

Ministry of Building, Innovation and Employment building performance and engineering manager Dave Gittings confirmed “an NBS rating is not a predictor of building failure in an earthquake”.

The quake-prone building system was based around “life safety risk” and low rating should be a “trigger for planning, funding and implementing a seismic upgrade, addressing the identified vulnerabilities and mitigating risk”.

Buildings that got different ratings from different engineers could result from one using different assessment methods, he said.

“NBS should be viewed as indicative of the engineer’s confidence in the expected seismic performance of the building rather than an exact prediction,” he said.

The system was due for a review in 2027 — a decade from the 2017 changes coming into effect — but could be triggered earlier if new information came to light or if requested by the Minister for Building and Construction.

The council and Wellington mayor Tory Whanau have been approached for comment.

*CORRECTION: The number of earthquake-prone building in Wellington is 572. An earlier version of this story had an incorrect number. (Amended, November 20, 2023, 11.29am)