"The building will actually be much better than 70 per cent, in my opinion, because we took no account of the previous strengthening."
The work, which features a steel exoskeleton on its rear walls, was carried out by Built Construction Group and engineered by NZCEL.
"We went to great lengths to preserve the Cuba Street streetscape so that wing of the hotel was shut down to guests and strengthened from the inside of the hotel rooms. This was challenging for business but preserving safety and history was the goal," said Nicholls.
To continue operating for guests, the rear wings were strengthened by bolting an exoskeleton of steel on the outside of the brick building.
"We needed to ensure these heavy walls wouldn't fall in or out. To do this we externally bolted 250mm steel channels to the wall."
In appropriate places the steel is bolted through the walls and is fixed into the floors, which have been made into diaphragms holding the floors square in an earthquake.
"As far as we know, this is the only exoskeleton building in the Wellington region or across New Zealand strengthened in this manner. The brick walls proved to be of very high quality and can take the earthquake movements in the direction parallel to the wall."
The re-strengthening work caused significant disruption to the hotel occupancy during the construction with the scaffolding putting some off despite the Hotel maintaining full compliance throughout the work.
"In an already competitive market this sort of elective work is hard on the business but we feel even more assured in the building's safety now – and that's what counts for our guests."
The scaffolding on the outside of the building lead some to believe conferences and other events were not still being held in the hotel, which was untrue, Nicholls said.
There were about 20 rooms out of action at any one time.
"It has cost us quite a lot of money in terms of lost income."
But he said it was "really good" to finally have the work done.
Meanwhile the Thorndon Hotel Wellington by Rydges already had strengthening work underway when the Kaikōura earthquake hit in 2016.
General manager Jeff Hermes said the strengthening work was interrupted by the quake, which led to a change in legislation of both New Building Standards requirements and local council targeted evaluation.
"These changes presented challenges to our construction methodology, meaning that more onerous calculation assessments had to be used," he said.
The owners made the decision to raise its NBS rating to greater than 80 per cent.
In total, $6 million has been invested in the seismic and refurbishment work that has been carried out at the Thorndon Wellington over the past two and a half years, including the drilling of 6573 holes and the addition of 2292 metres of steelwork, with a formal re-opening set for December 6.
Owner HC Tan said the finished product is a result of meticulous planning, with involvement from well-respected consultants, builders and staff.
"Despite facing unexpected delays and challenges, the whole team has carried on with remarkable creativity and perseverance, and the end-result today is both structurally resilient and aesthetically pleasing," he said.
