Ten organisations have launched probes into the cause of the fire. Photo / NZ Herald
News that no fewer than 10 different organisations are now investigating the blaze that devastated SkyCity's new convention centre has thrown up a raft of questions about what went wrong.
Yesterday, the Herald reported that part of the inquiries now underway would look at supervision and experience of the workers on the roof.
The Herald has been told a young worker, employed by a subcontractor, was called for a smoko break and forgot to turn off a gas blowtorch that was being used to help install a waterproof membrane on the building.
It's understood he was returning to the roof to check the blowtorch but by then the fire had started.
The Herald looks at three big questions that still surround the event.
With the calamity still under investigation, various industry groups approached by the Herald were reluctant to comment on what rules might have been breached before the fire broke out.
But they did point out there were plenty of protocols in place to avoid such a risk.
Under the Health and Safety at Work Act, companies were required to manage risks arising from their work.
There were no prescriptive rules in the law about how to manage the risks around "hot work" like welding and cutting, but it was common practice in the industry to operate a "permit to work" system.
Fletcher Construction, the company managing the $700 million build, had such a system in place, and this included permits specifically for hot work.
While these detailed permits could be customised depending on what's being carried out, there were many baseline requirements involved when it came to fire danger.
Guidelines under Standards New Zealand's code of practice for safety in welding and cutting said any nearby combustible materials should be prevented from ignition.
Fire-resistant shields had to be used to confine the heat, and a chief fire warden or principal supervisor needed to have inspected the work area, confirming that precautions had been put in place and that a permit had been issued.
Only workers with appropriate levels of competence and skill were allowed to carry out welding work, and not use equipment they weren't certified to.
Installing a "torch-on" membrane system was done by using a gas torch with a naked flame to heat the bitumen content of a sheet, which then fixed in place the layer immediately beneath.
Under the specific code of practice for installing these systems, workers were expected to "cease all torch-work in areas of concern at an appropriate time prior to leaving the site to ensure continued site safety".
Further, the code stated that all such work had to be carried out by "competent, experienced" personnel.
Construction was also regulated under the Building Act 2004, which required that work should comply with the project's building consent and the Building Code.
Kevin Frank, a fire research engineer at BRANZ, considered fire a "relatively common" risk during construction.
Buildings were particularly vulnerable during construction because not all of their fire protection measures had been put in place – as was the case with a sprinkler system that hadn't yet been commissioned at the centre.
On top of that, hot work activities were common and involved potential sources of ignition, Frank said.
"The risk is best managed by implementing and adhering to good processes.
"Establishing fire protection measures like fire separations and sprinkler systems as soon as possible can help," he said.
"Implementing a fire watch, particularly during and after hot work processes, can provide early detection and prevention."
It wasn't clear whether the contracted company was using a fire watch itself.
There has been much focus on the bitumen material that formed the building's membrane and was set alight during the fire.
Often used in near-flat roofs of multi-storey buildings, this material was comparable to that of tar used on roads, and while combustible, was still difficult to ignite.
The Roofing Association of New Zealand said there were "significant quantities" of such torch on products used around the country without incident.
Engineering expert Professor John Tookey, of Auckland University of Technology, said the specific system of boards and bitumen sealant used at SkyCity wasn't new.
"I remember my father used a very similar system to put the roof on a garage in the 1970s, when it was similarly not new then either."
But there have also been questions around why Fletcher Construction chose to use panels in the roof that contained compressed straw insulation.
University of Auckland Associate Professor of Civil Engineering Charles Clifton, who consulted on the building's fire risk, suspected the straw was chosen over other forms of insulation for environmental reasons and also because the material it was less toxic in fire.
When he was shown details during a tour of the roof, the company told him they were "very aware" of the potential combustibility of the straw and ply during construction if a fire broke out, and were taking precautions to prevent it.
Tookey believed the principle issue at stake in the legal saga to come would likely be interpretation of the regulations.
In particular, he said, it would come down to interpretation of a "reasonable" adherence to the regulations.
"Specifically, adherence in terms of oversight and supervision of anyone involved directly in the process," he said.
"And thereafter adherence to the requirements of 'soak' time after use of the torch has finished and when the overwatch of the works stopped."
Conversely, he added, if the issue of "reasonable" is at stake, it was likely that the accompanying issue of "negligence" would raise itself.
"'Reasonable' behaviour results in lighter penalty. 'Negligent' behaviour, by contrast, results in immeasurably heavy consequence."
In any case, expected the process to "run and run".
"I have no doubt that the immediate parties of client and contractor are most likely to be fully covered. However, who shoulders the bulk of the financial payout burden is likely to be contentious to say the least. There is a huge value at risk here for all parties."
This, in turn, tended to militate away from immediate acceptance of responsibility, he said.
"In a worst-case scenario – dependant on proven liabilities – the future of various contractors and insurers is potentially at risk. The issue of liability will almost certainly be tested in court in some form. The likely protagonists will be the various insurers involved.
"It is not hard to imagine that reasonableness and negligence will similarly end up subject to legal interpretation too. Specialist consultants will be called. Documentary and video evidence will be reviewed at length.
"Needless to say, not a happy situation for anyone. Not something that will be resolved rapidly.
"Ultimately there are no winners from this situation."
Former Act president's lawyer claims sentence was too harsh, calls for home detention.