More Christchurch buildings marked for demolition

Another 123 buildings in Christchurch have been approved for demolition or partial demolition. Photo / Brett Phibbs

Another 123 buildings in Christchurch have been approved by Civil Defence for demolition or partial demolition - or are required to be made safe, bringing the total to 307.

The latest demolition list announcement comes as engineers are calling for a rethink on how we build our cities ahead of a conference on earthquake engineering set to kick off in Auckland tomorrow.

Of the additional buildings, 87 buildings are up for full demolition, 28 partial demolition and eight requiring work to be made safe. The additional buildings include another 25 heritage buildings.

Most of the 307 buildings on the lists are outside the red zone in the central city.

Civil Defence National Controller John Hamilton said the list is expected to grow by several hundred over coming weeks as more buildings in the red zone are added.

"The decision on what to do with a particular building involves many different groups, including owners, insurers, tenants, building or demolition experts, local and in some cases, central government.

"Many different factors need to be taken into account, such as safety - which is paramount - cost, the potential impact on surrounding buildings and businesses, time scales, asset recovery, access to business critical material, and plans for the surrounding area."

Meanwhile, engineers are calling for a rethink on building design in the wake of the devastation in Christchurch after the February 22 quake.

The Pacific Conference on Earthquake Engineering, which is held every four years, will take place over the weekend in Auckland.

Dr Andy Buchanan, Professor of Civil and Natural Resource Engineering at Canterbury University, said "lots of buildings in the Christchurch earthquake behaved exactly as expected, but they still ended up buggered".

"We designed buildings to withstand earthquakes with the expectation that they would be damaged. Unfortunately, many were damaged so badly that they will have to be pulled down," he told the Science Media Centre.

"Looking to the future, what we have to do now within the research community is to start designing buildings so that no matter how big the earthquake, buildings won't be damaged. This is the new paradigm. There are ways of doing this. We know how to do it, we just haven't started doing it yet."

Associate Professor Greg MacRae, an earthquake engineer at Canterbury University, told the Science Media Centre the most important factor to consider when rebuilding the city was seismic sustainability.

"At the moment we are building to protect lives, which means after a major earthquake like this, we expect this kind of damage," he said. "We can change our focus, and build to protect our infrastructure as well, using advanced technologies that are available for all materials.

"People have a choice. They can design and rebuild using 1980s technology, and they'll get the kind of results we've seen. Or they can use modern technology and get very little damage.

"Some of these new technologies cost the same or less than existing construction techniques. Some of these, like base isolation, have been around for a number of years and are well-proven. Some are less robust, and require more extensive testing and research.

"However, when you've got that choice, I think it's a no-brainer. The barrier to implementation is largely ignorance. A lot of it has also been lack of will. People have never really believed that an earthquake could occur here in Christchurch."