Up to 65 Wellington buildings could have the same potentially fatal weaknesses as Christchurch's CTV building, which collapsed killing 115 people.
The buildings, designed between 1982 and 1995, are among 158 identified nationally as possibly being built using non-ductile - or brittle - reinforced columns.
Wellington City Council has written to the owners of the suspect buildings, asking them to get detailed engineering assessments. It has refused to identify those buildings.
More than half the 185 people who died in the February 2011 Christchurch quake were killed in the CTV building.
Investigations into the collapse prompted the former Building and Housing Department to look at records of 1364 multistorey buildings built about the same time and to the same standards.
The department has since been merged into the Business, Innovation and Employment Ministry, whose earthquake communications manager Susan Owens said 158 buildings were identified as requiring further investigation, including 65 in Wellington.
Wellington City Council earthquake resilience programme director Neville Brown said that did not mean they were all necessarily a risk. But where strengthening work was needed, the council would work closely with owners to ensure the work was done as quickly as possible.
“The style of reinforced concrete construction identified by the Department of Building and Housing was used in the 1980s and 1990s around the country - the building standards of the day permitted this type of design," Mr Brown said.
However, structural engineer Adam Thornton said most Wellington buildings of the era had more reinforcing put into them than the codes required, because the city was known as having a higher earthquake risk.
The key thing was spiral reinforcing. Columns were less brittle if they had steel hoops or spirals to confine the concrete, so it was less likely to break in an earthquake.
Where brittle columns were identified, it was relatively easy to strengthen them by wrapping them with steel plates - as was done with the Wellington motorway columns - or by wrapping them with carbon fibre.
The ministry would not name the buildings with suspect columns.
Council spokesman Richard MacLean said: "The reason we're not giving out the list is for the same reason we don't publicly list any potentially quake-prone buildings. We don't want owners and occupants to worry that a building may be quake-prone when the case may well be that it isn't."
Ms Owens said: "It is not in the public interest . . . to publish a list at this time. Even though these buildings have been identified as requiring detailed engineering assessments, there might not be an issue, depending on the design of the building."
Many suspect Wellington buildings were built during a boom in the 1980s and early 1990s. One that has been previously identified is the Greater Wellington regional council building in Wakefield St, which has been assessed as meeting only 30 per cent of the current building standard.
Buildings of similar vintage include the city library and adjoining office building, and many other suspect buildings are dotted around the city.
Wellington property investor Eyal Aharoni, who owns many city office blocks, said the council had asked him to look at the Stout St car park, which he owns. He had asked engineers to check it out.
One of the main flaws in the CTV building was that its columns were too brittle: its reinforced concrete columns had insufficient steel reinforcing to stop them crumbling and collapsing in the February 2011 earthquake.
The building and housing group in the Business, Innovation and Employment Ministry is worried that 158 other multistorey buildings built to the same standard between 1982 and 1995 could also be at risk.
Sixty five of these are in Wellington.
WHAT IS HAPPENING NOW?
Building owners have been asked to get engineering checks done.
HOW CAN THEY BE FIXED?
Columns can be wrapped in steel plates or carbon fibre blankets. This will reinforce the columns and make them less brittle.
- © Fairfax NZ News
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