Govt confirms overloading cause of Dunedin balcony collapse

The balcony collapse (Newshub.)
The balcony collapse (Newshub.)

A Government investigation into the Dunedin balcony collapse earlier this year has reiterated the cause was overloading.

The Ministry of Business, Innovation and Employment opened an investigation into the collapse of a Castle St balcony during a music concert last month.

Several students were injured including two who suffered serious injuries.

Building and Housing Minister Dr Nick Smith says the report found the balcony met Building Code requirements.

"The simple reason this balcony collapsed was that nearly twice the number of people it was designed to support were on the balcony, and many of those people were grouped at one end of it," he says.

The investigation has found the balcony ... was properly consented, was built to standard, and received a Code Compliance Certificate."

"Inspection and testing of the joists that failed has not identified any concerns about the standard of timber used in the construction."

Dr Smith says the lesson from this incident is for people not to use residential balconies as grandstands.

"They are designed for a loading of two kilopascals (kPa), or about two people per square metre, and crowding more than this poses risks for the people on them and others."

Another lesson he says is for people to co-operate with police and other officials in the interest of public safety during events such as a concert.

"Crowds can pose additional risks that may not be obvious to people having a good time," he says.

Officials have been asked to undertake additional work on two technical areas to ensure buildings are constructed as safely as possible.

"I have asked officials to review the buildings loading standard [NZS1170] in respect of residential balconies that have a risk of being crowded because of their context and surrounds."

The code currently provides for 1.5kPa on decks less than a metre off the ground, and 2kPa for standard residential decks, but 4kPa for balconies used for community activities and 5kPa for sports stadiums, Dr Smith says.

"There are environments, such as on streets commonly used for street parades or in close proximity to concert venues, where it may be justifiable to require the higher loadings."

The second technical area was the building practice of notching structural timber. The joists supported the balcony were reduced from a 200 x 50 millimetre depth to 150x50 millimetre depth at the interface with the building.

"This was quite within the Code, but is a building technique some timber engineers are concerned may create stress weaknesses," he says.

Dr Smith welcomed the proposal by Dunedin City Council and the University of Otago for a review of the event which led to overcrowding.

He says now we know the building standard was met, progress needs to be made to stop this sort of accident happening again.

The proposed review will also provide an opportunity for the students at the event, and those injured, to have input into how these events could better managed in the future.

"Structural failures of buildings in New Zealand are thankfully rare but when failings occur we do need to heed every lesson possible," Dr Smith says.

"This investigation may result in some technical revisions to the Code, but the most powerful lesson is that buildings should not be used for purposes they were not designed."