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The collapsed stairwell in the Forsyth Barr Building - Source: ONE News -
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Concerns over the strength of the stairs in a Christchurch office block had been aired months before they collapsed in last February's earthquake.
The Royal Commission of Inquiry into the Canterbury Earthquakes heard today how workers in the Forsyth Barr building had become concerned about the stairs after the quake in September.
"It was clear that they had sagged somewhat as the paint on the wall had separated from the stair treads for most of the lengths of the flight," office worker Grant Cameron said.
When the earthquake struck on February 22 the stairs collapsed, leaving workers stranded.
"There was just a gaping hole stretching down the middle of the building with blackness both above and below," Cameron said.
"It was now plain that everybody was now trapped on their respective floors."
The stairs were compressed and failed catastrophically as the built-in 30mm seismic gap - designed to allow movement during quakes - was overwhelmed.
No one was in the stairwell at the time of the quake, but the Commission heard if there had been anyone there, they would have probably been killed.
Despite the concerns of workers the building was given a green sticker and recommended safety checks were never carried out.
"I was surprised when we learnt that not much had happened with the stairs in that intervening period," engineer Rod Jury said.
"To me, and we walked the whole building, that was probably the main issue."
The Building and Housing Department has since issued a warning about all buildings with the same "scissor" staircase design.
However the inquest heard retrospective strengthening work on similar staircases would be costly and alternative designs should be used in future buildings.
The two day hearing into the Forsyth Barr building problems wraps up tomorrow.
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