Property Council wants building code rethink

12:49 pm on 3 March 2011

The Property Council wants the building code and earthquake standards re-evaluated after what happened to some Christchurch buildings in last week's earthquake.

Chief executive Connal Townsend says some reasonably high standard buildings were severely damaged while others, which were only at a third of the required earthquake standard, were left relatively unscathed.

He told Nine to Noon the approach used by city councils when they assess buildings varies, though most councils require them to meet one third of the modern building standard.

Mr Townsend says issues which are emerging about soft soil and liquefaction are things which the current earthquake code simply does not deal with.

GNS Natural Hazards manager Kelvin Berryman says he'd be surprised if it emerges that constructing modern large commercial buildings on soft soil is a significant problem.

Reports by Quotable Value show the Pyne Gould and Canterbury Television (CTV) buildings were built on soft soil.

Mr Berryman said the soft soil phenomenon is well known and large modern buildings always have a specific foundation investigation and treatment.

He says there might be more of an effect on residential buildings, which don't have a specific design for every building, or on older buildings.

Quotable Value says its reports mean a strong close-by quake could cause moderate increase in shaking to the CTV, and a large increase in shaking to the PGC. They also show the sites were prone to liquefaction.

Quotable Value says the reports are based on geological modelling and do not supersede enginering or a specific site inspection.

An inquiry will be held into why the Pyne Gould and CTV buildings failed to withstand last week's earthquake, as well as looking at broader issues including whether the building code is robust enough. Both buildings were given green stickers after the September earthquake, meaning they had passed an external check.