Vehicles in the car park may have started the fire that engulfed the Canterbury TV building, the Canterbury Earthquakes Royal Commission has heard.

The CTV tower collapsed in the February 22 2011 earthquake, killing 115 people. The fire hampered rescue efforts.

Counsel assisting the royal commission, Stephen Mills QC, told the hearing the CTV tower collapsed “in a manner of seconds”.

“Not only did the building collapse extremely rapidly, it collapsed almost completely,” he said.

Only one person survived from levels one and two – the CTV receptionist who ran from the building just before it collapsed. The largest group of survivors was on the top floor, level six. These people could “virtually walk out at street level”.

The royal commission has heard considerable evidence about whether the structure conformed to building standards.

People who worked there have detailed damage from the earlier September 2010 earthquake and Boxing Day 2010 aftershock.

Margaret Aydon said the floor on level 4 was uneven. “We had to use Blu-Tack or rubber bands on my pencils and pens to stop them rolling off the desk,” she told the royal commission.

She said staff continued to ask about earthquake damage but were told the building had been inspected and was safe.

CTV receptionist Maryanne Jackson said she and other staff did not feel safe after the September quake. Many ran outside every time there was a major aftershock.

They could see daylight through the cracks in some walls and the floor moved when people walked down a corridor.

Fletcher Construction Chief Engineer Graham Frost, who assisted the Urban Search and Rescue team after the February earthquake, said at least six vehicles were removed from the car park. All were burned out.

“I think it is possible that the fire may have started in these vehicles, providing a fuel source for some time,” he said.

Mr Frost said three very brittle/non-ductile failures could have triggered the collapse or contributed to its scale.

These were the failure of beam-column connections, failure of the bond between the metal decking and the concrete floor slab and tension failure in the metal decking.

Forensic structural engineer Robert Heyward was part of a Queensland taskforce involved in the search and rescue. He said the concrete disintegrated into rubble more readily than he would have expected, which indicated poor tension strength.

He said ductile structures are desirable in earthquake regions because they can bend before they fail, giving occupants some warning, while brittle structures are like a stick of chalk, which is brittle when bent. 

Mr Heyward said the building collapsed quickly, with many elements becoming detached from each other.

Elements that may have contributed to the brittle nature of the collapse included the columns, beam-column connections, and the connections between the floor slabs and the south wall and north core.