A structural engineer says analysis of the collapsed Canterbury Television building could have gone on forever, but those investigating the cause of the failure had to draw the line somewhere.
The Canterbury Earthquakes Royal Commission is looking into a Department of Building and Housing report completed earlier this year that found the CTV building had major construction and design flaws.
The building in central Christchurch pancaked during the devastating February earthquake in 2011, killing 115 people.
Rob Jury, a member of the expert panel that oversaw and approved the report, told the commission on Tuesday he is comfortable that enough analysis was done, but there is a chance that something was missed.
"It is possible to go on refining, but I think it becomes a diminshing returns exercise. But it does not preclude the fact that something could be done that would come up with some totally earth shattering result that would change everything."
Mr Jury said the final conclusion was that the CTV building's columns failed.
He then defended the general nature of those results, saying different experts came up with their own scenarios and the trigger of the collapse is uncertain.
Vibrations not a factor - engineers
Earlier, two engineers that prepared the report on the CTV building said vibrations from nearby demolition work would have had little effect on its ability to resist earthquakes.
The Royal Commission questioned Dr Clark Hyland and Ashley Smith on Tuesday about the report for the Department of Building and Housing.
Lawyer Marcus Elliott, representing families of those who died, asked the engineers whether the report placed enough importance on the effect of vibrations from demolition work being done on a structure close to the western side of the CTV building.
Mr Smith said while some demolition techniques were used without the Christchurch City Council's approval, the vibrations would not have affected the building's seismic resistance.
"We are aware that they used procedures in the demolition that weren't approved, including a wrecking ball which would have caused stronger vibrations, but we still have the view that that did not impair the seismic resistance."
Mr Smith said before the building's collapse, tenants would have been very sensitive to vibrations and may have placed too much significance on them.
He said there may be a perception that the report did not take the effect of the vibrations seriously enough, but the topic was given appropriate coverage considering that the vibrations were not a major concern.