Pace Project Management director Andy Christian said all but the upper two floors of stairs collapsed in the February 2011 earthquake, leaving seven flights of reinforced-concrete stairs perched precariously above the empty stairwell.
"Engineers rated this a serious drop hazard, preventing further investigative work on the building from taking place near the stairwell," he said.
"So getting these flights out was a top priority.
"We had to adopt a complicated method to remove them by propping each flight with a temporary steel frame, then cutting them in half and lifting sections out through the roof using a large crane."
The task was one of the most difficult and time-consuming of numerous commercial building projects undertaken by the company in the city's badly damaged central business district.
Mr Christian said rapid progress could now be made on a full engineering inspection of one of the few remaining high-rise buildings in the CBD.
"It needs to be determined what repairs will be necessary to reinstate it to the required building code.
"When completed, a repair schedule will be drawn up for costing and if it proves to be economic, the building could be available for re-occupation in about 18 months."
