The prime Wellington waterfront office block at 36 Customhouse Quay is being ‘unwrapped’ after extensive earthquake strengthening, revealing exterior steel supports never-before seen in Wellington.

Scaffolding has started coming down around the Cornerstone-owned office building after a two year earthquake strengthening and complete refurbishment programme, undertaken by contractors McKee Fehl.

Chief Executive Andrew Cotterrell says Cornerstone has invested heavily to improve the expected seismic performance of the building and bring it in line with modern structural design philosophies, with one notable addition being the external steel ring brackets around the columns at the four corners on the upper levels of the building – a solution he believes is world-leading, and unique.

“You wouldn’t see a single other building in Wellington that has rings around the outside of the columns,” Andrew said. “It’s highly visible and innovative.”

The steel rings and steel arms coming off them have been used to add strength and resilience to the connection between the beams supporting each floor and the external corner columns to remove any uncertainty about the post-earthquake capacity of reinforcing steel rods internally connecting the beams and columns.

“Like a paperclip, the reinforcing steel rods can only bend and flex a number of times before they will become over-stretched and snap, and we wanted to be certain about the resilience of those connections after the Kaikoura Earthquake,” Andrew said.

“Having investigated it, there remained some uncertainty around whether the steel at the corner beam and column connections had stretched to its capacity. We wanted to eliminate any doubt so we worked with our engineers, Holmes Consulting, and a peer reviewer to come up with a unique solution. You could argue it is overkill, like putting a plaster-cast on an arm that is not broken, but we decided to do it because we care about our buildings and our tenants.

“No-one has ever queried these beam to column connections before because you can’t see the reinforcing steel rods inside so there is no way of knowing how much capacity is left, but if it has been over-stretched the risk is that the reinforcing steel rods could snap in another big quake.”

Cornerstone was already well underway with a seismic strengthening programme at 36 Customhouse Quay before the Kaikoura Earthquake. The installation of all of the external steel beam to column brackets was completed in November and final work is now being done on a car parking floor and exterior awnings as part of the original strengthening programme. The owners expect all work to be complete and the final scaffolding to be down in the first quarter of 2019.

The 1980s constructed building is 13 floors of prime waterfront commercial office space and one floor of residential apartments on the top of the building.

Andrew says Cornerstone has worked closely with tenants to keep the building tenanted throughout the strengthening programme, with just the fifth floor being kept vacant to rotate tenants onto as strengthening work moved through the other floors.

There has been strong interest from prospective tenants in the fifth floor and it is likely to be let early in 2019.

“There is high demand along Customhouse Quay with the great location and water views, and interest is particularly strong because most businesses are very seismically focussed now. They don’t want to be at risk and they don’t want to put their people at risk. There has been a flight to quality after Kaikoura.”

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