The former home of a Wellington gentlemen's club with one of the lowest earthquake ratings in the city is being strengthened with base isolators, joining the ranks of Te Papa and Parliament.
The Wellesley Club on Maginnity St is a five-storey neo-Georgian building that was built between 1925 and 1927 to house the gentlemen's club of the same name.
The building is now the home of Westminster Masonic Lodge and the Wellesley Boutique Hotel.
An earthquake prone notice issued by Wellington City Council states the building is just 3 per cent of the New Building Standard (NBS).
Anything less than 34 per cent NBS is considered earthquake prone.
The original plan was to strengthen the building by bolting it to the adjoining former Defence Force headquarters, but that never eventuated due to timing and joint-ownership funding issues.
But now the building is fully owned by the Westminster Consortium and the decision has been made to install about 20 base isolators to bring the building up to 100 per cent NBS.
Exactly how much the project is going to cost is still unknown but it will be at least $5m.
There are about 40 buildings in New Zealand which have base isolators including Parliament, Te Papa, and Wellington's new children's hospital.
Base isolation works by putting flexible bearings or pads between the building's foundations and the structure above.
The base isolators move and absorb the impact of the earthquake, protecting the rest of the building from swaying and shaking.
Stuart Brooker, a Westminster Consortium director, said base isolation was the only strengthening option left for the Wellesley building.
The building is almost dwarfed by another on the adjoining block housing the Ministry of Business Innovation and Employment, and the fear is the two would likely clash in a major earthquake.
"It's the only thing as far as we're aware that will protect us from the building next door unless we're bolted onto it in which case when it moves, we move with it.
"We can't demolish and rebuild. It's a Category 1 heritage building and we love it, that's why we bought it."
According to Heritage New Zealand the building originally followed the form of the English gentlemen's club.
It featured a billiard room, card rooms, reading rooms, lounges, bars and dining rooms. In addition, the upper storey included bedrooms.
Gray Young designed the building for which he won the New Zealand Institute of Architects Gold Medal in 1932.
Brooker said the consortium was in a good position at the beginning of this year to get a loan from the bank for strengthening, but they were now having to nurse back to health the hospitality business housed in the building following Covid-19.
Despite the building only having a 3 per cent NBS rating, Brooker said he was confident the structure above ground was strong.
"If our building falls down in an earthquake, so will half of Wellington … the fact that the building has stood there for 100 years speaks for itself."
Brooker said the only damage the building has sustained in any earthquake is surface cracking on the interior walls.
There are some buildings in Wellington which have an even lower rating, for example, 116 Cuba St is rated at just 1 per cent NBS.
These low NBS ratings were determined by a process called an Initial Evaluation Procedure (IEP).
Wellington City Council chief resilience officer Mike Mendonça said this was based off an exterior assessment of the building and its plans.
He described it as a "fairly blunt instrument" but nevertheless a screening tool to get through thousands of buildings the council was tasked with assessing.
Building owners then have the opportunity to challenge that initial assessment with a detailed seismic assessment.
"Most of them do that and sometimes that gets them off the earthquake prone building list, but if it doesn't, at least it tells them what needs to be done, Mendonça said.
"All these ones in the single digits were done on an IEP and almost exclusively it's where the owner decided not to challenge and to crack on."
Brooker didn't bother getting a reassessment because he knew the building would still be considered earthquake prone even if the rating did increase slightly.
The deadline for strengthening the Wellesley building is 2025.