No more high rises for rebuilt quake city

The glass wall of the Christchurch Art Gallery was designed as a 'frame within a frame' to resist movement. Photo / File photo

Architects believe no more high-rise buildings will go up in Christchurch after last week's earthquake.

"The height of the city will drop," said Peter Marshall, managing director of Christchurch-based Warren & Mahoney.

Architects spoken to yesterday also expect tougher national standards for strengthening older buildings, potentially affecting thousands of buildings throughout the country built before earthquake codes began to tighten during the 1970s.

The Department of Building and Housing's deputy chief executive for building quality, Dave Kelly, said the department's regulators would clearly have to look at the current provision for councils to adopt policies to bring older buildings up to one-third of the strength required in modern buildings.

"The current situation is that local authorities have the responsibility for setting a policy around the timeline," he said.

"I'm sure all the local authorities in New Zealand will be turning their mind to that."

Mr Marshall, whose firm designed many of New Zealand's iconic buildings including TVNZ in Auckland, Wellington's Michael Fowler Centre and the Christchurch Town Hall, is determined that Christchurch will rise again.

"When one says a quarter of the Christchurch buildings are at risk, that means three-quarters of the buildings are not at risk," he said. "When people say 1000 people are leaving daily, that means 300,000 are staying.

"Look around and the people are here. Look around and the buildings are here, and people are trying to make sense of it and make it work."

He said most modern buildings performed well in an earthquake that was twice as strong as they were designed for, but architects had to accept that people simply would not want to work in high-rise towers any more.

"I think in Christchurch in our lifetime there will not be any multi-storey buildings built."

He said the council would also have to take the hard decision not to allow rebuilding in areas with the worst liquefaction.

"We are going to have to relocate one or two suburbs," he said. "We have the land to do it. Rolleston and Pegasus [in the west] have been fine in both earthquakes."

Architects and engineers had techniques to build on unstable ground, but they were expensive. His firm designed a seven-storey apartment block three years ago on the water's edge at Ferrymead which withstood the earthquake despite the ground conditions.

"We knew it was prone to liquefaction," he said. So they drilled down 12 metres to find bedrock, poured stone into the drill holes and compacted the stone."

Mr Marshall also worked on the strengthening of Parliament in Wellington where the whole building was floated on a rubber base designed to isolate it from ground movement. But that cost $100 million.

"We must identify our critical heritage buildings and take all steps to save them," he said. "In Christchurch you could say definitely the cathedral."

An Auckland architect who designed the glass wall of the Christchurch art gallery, Stephen Thurman, said it survived the quake because it was designed as "a frame within a frame" which isolated it from ground movement.

But Richard Harris, immediate past-president of the NZ Institute of Architects, said Christchurch and the nation would need to decide which buildings were worth spending such public funds on.

"I think we are going to have tougher standards," he said.

"And we may have to be more selective in what we keep because of the cost."