Roof collapse raises building code fears

Scotts Ferry resident John Ransom on the stopbank that saved the town from flood water. Photo / Mark Mitchell

A leading structural engineer says New Zealand's whole engineering system may have to be reviewed after last Saturday's roof collapse at Invercargill's Stadium Southland.

Dr Charles Clifton, an associate professor at Auckland University, said a commission of inquiry might be needed, similar to one in Canada after the opening-day collapse of the Station Square shopping centre roof in Burnaby, British Columbia, in 1988.

"We may well be facing our own Station Square coming out of this," he said.

The Southland collapse came after design faults had to be fixed during the construction of Vector Arena and Waitakere Trusts Stadium several years ago.

"Our track record with large long-span roofs has not been particularly good," he said.

Another Auckland structural engineer who wrote an open letter on widespread design faults in 2002, John Scarry, said the situation had worsened since then.

"There has to be a change of legislation and something like an engineering commission set up to sort things out from first principles," he said.

But the Institution of Professional Engineers (Ipenz) board, which met in Auckland yesterday, warned against jumping to conclusions before the full facts about the Southland collapse were known.

Chief executive Andrew Cleland said Ipenz was waiting for investigations by the Department of Building and Housing's chief engineer Mike Stannard and Graham Cole, a local engineer appointed by Invercargill Mayor Tim Shadbolt.

Building Minister Maurice Williamson visited the collapsed stadium yesterday and was reported as saying that the roof complied with the building standard for snow load that was in place when it was built in 2000.

The standard was upgraded with higher requirements which took effect in 2008.

Dr Cleland said the MetService would need to determine the likely weight of the snow on the stadium roof, and the amount of wind which could have heaped the snow on certain parts of the roof, after what was said to be the area's heaviest snowfall in 50 years.

Ipenz president Garry Macdonald said yesterday's board meeting discussed whether the snow loading code should be reviewed in the light of the weekend's extreme conditions.

Dr Clifton said he believed the investigations were likely to find that the stadium was poorly designed or built, or both.

"If this stadium collapse is found to be the result of significant design errors or procedural errors or both, then I think we will probably get the review that John [Scarry] has been pushing for for some time. It's a high-profile building and there will be forced on to the profession a review of the whole system."

Dr Clifton said many engineers were quoting such low fees to get work that they could not provide the design and monitoring required to make sure buildings were safe.

"In quite a few designs fees are too low to provide the level of resources and service that the project requires, and it is generally known that we are operating at a minimum or less-than-sustainable fees level," he said.

He said some engineering firms also failed to give new graduates the on-the-job training and mentoring required to put their academic training into practice.