One in three Christchurch buildings may come down - PM

An aerial view of emergency services working at the ruined CTV building in central Christchurch. Photo / Sarah Ivey

One in three commercial buildings in the centre of Christchurch may be demolished after last week's devastating earthquake, says Prime Minister John Key.

For every one of those buildings to be demolished, geotechnical work would have to be done on the land, possibly with deep piles to reach solid ground, Mr Key told NewstalkZB today.

"We are talking two years before you see very much, five years you will see quite a bit, 10 years you will see a lot."

The rebuild of Christchurch would be "a 15-year job", he said.

Buildings constructed under modern building codes could survive without damage and that was shown by the Inland Revenue Department building across the road from the CTV building in which around 100 people are thought to have died when it collapsed.

"The lights are on, it is a normal glass building. Not a pane of glass broken, it is in perfect condition," Mr Key said of the IRD building.

With a third of the buildings in the central business district under threat of demolition, Christchurch might develop as a city with large satellite business districts.

- NZPA