Keeping Buildings Earthquake Safe

New Zealand is extremely prone to earthquakes. In 2018 alone there were almost 20,000 earthquakes across the country. While residents may only have felt a small portion of those quakes, the risk of another big earthquake like the ones in Christchurch and Kaikoura should not be taken lightly.

On 1 July 2017 – six months after the Kaikoura earthquake – a new national system for managing earthquake-prone buildings in New Zealand came into effect.

Following the implementation of the new system, properties like James Cook Hotel Grand Chancellor, Amora Hotel Wellington, and the Thorndon Hotel Wellington, among others, closed temporarily for seismic strengthening work.

Building NZ defines an earthquake-prone building as a property that in the case of a moderate earthquake could potentially collapse, and if it collapsed it would do so in a way that “is likely to cause injury or death to persons in or near the building”. It also changes how new buildings are designed.

“Earthquakes and seismic activity are considered as loads imposed upon buildings and the resistance of seismic loads is now factored into the structural design of new buildings,” said Nick Hill, chief executive of Building Officials Institute of NZ.

“In terms of requirements, the Building Act regulates building work, requires new building work to comply with the Building Code and specifies when upgrading is required.”

New Zealand has a system that categorises the country into low, medium and high-risk seismic areas which determines the time for assessing and doing seismic work on properties in earthquake-prone buildings.

New Zealand is sorted into High, Medium and Low-risk seismic areas.

This process starts with local councils who identify buildings as earthquake-prone and then inform the owners. The owners must then get engineers in to assess the building, and then report back to the council whether the property is safe or needs strengthening work. The council looks at the report and then work can commence if necessary.

The information the engineers get from assessing the building is used by the council to determine a building’s earthquake rating in line with the New Building Standard. The two categories of earthquake risk are:
• 0 percent to less than 20 percent in line with the New Building Standard
• 20 percent to less than 34 percent in line with the New Building Standard

Thorndon Wellington was one hotel that was affected by the new earthquake-prone buildings laws. While the hotel had been working on seismic strengthening since 2015, when the Kaikoura earthquake hit it had to double down on its strengthening plans and wasn’t able to reopen until November 2018. After the works, Thorndon Wellington became the first Wellington hotel to complete seismic strengthening and raise its NBS rating over 80 – the equivalent of an A grade.

The Ministry of Business, Innovation and Employment oversees New Zealand’s building system and wants all potential earthquake-prone buildings in high seismic-risk areas identified by 1 July 2022.

In some cases, there are exemptions. For instance, if the council is satisfied that the building and its surroundings will have minimal to moderate occupancy and collapse is very unlikely in the case of a moderate earthquake and a transport route is unlikely to be blocked if the building does collapse.

Additionally, earthquake-prone heritage buildings can apply for an extension of up to ten years to strengthen their buildings. For this to happen though, the building has to be Category 1 on the New Zealand Heritage List or included on the National Historic Landmarks List.

A recent example of this is the Rydges Lakeland Resort Queenstown which was scheduled to close two earthquake-prone wings of its property by the end of February but delayed until March 17 as the hotel has 15 years to meet the seismic standards and can do its strengthening work any time inside that window.