A trauma counsellor working in Christchurch's CTV building experienced a falling sensation but was "gobsmacked" when she was pulled from the wreckage at ground level.
Nilgun Kulpe has told the Canterbury Earthquakes Royal Commission hearing on Monday of a violent upwards movement in the February 22, 2011 earthquake.
She was sitting on the top, sixth floor and was propelled upwards. She felt the building twist sideways and was able to see the outer walls had fallen inwards.
By chance she and her colleagues were using a different room that was close to one side of the building. If they had been in their usual room they would have died, she said.
Instead they came down as if in an elevator, jolting to a stop.
"When I finally looked out I was completely gobsmacked that we had travelled all the way down," she said.
Of the 185 people who died in the earthquake, 115 were in the 25-year-old CTV building.
Before the February quake and following the earlier big ones of September 2010 and Boxing Day 2010, Ms Kulpe had been stressed and scared.
"I felt like the building was sick and that it wasn't safe. In the aftershocks I would always go to the nearest door frame," she said, adding that was embarrassing when she was trying to calm traumatised clients.
The building moved and shuddered from the fitness classes in the gymnasium next door.
These movements became worse as the adjacent building was demolished.
Before she gave evidence, the royal commission's lawyer, Stephen Mills QC, outlined the sequence of witnesses who will appear over the next eight weeks.
Central to the commission's investigation would be the evidence heard from Alan Reay Consulting, the company that was responsible for structural engineering.
Witnesses called by Alan Reay would proffer alternative explanations about a number of issues such as concrete strength and the veracity of supporting columns, Mr Mills said.
A Department of Building and Housing investigation had found the strength of the columns and the asymmetrical layout of the supporting walls did not meet the building standards when it was built in 1986.