A civil engineer says an official report into the collapsed CTV building was a waste of time and taxpayer money.
The Canterbury Earthquakes Royal Commission of Inquiry is investigating why the CTV building failed in the 6.3 magnitude quake on 22 February, killing 115 people.
A New Zealand civil engineer working for a Texas university, John Mander, has been called by the building's designers, Alan Reay Consultants, to give evidence to the inquiry.
Professor Mander told the inquiry on Monday the report, commissioned by the Department of Building and Housing, was neither useful nor insightful.
He said conclusions drawn by the report's author that the building collapsed after concrete pillars became overloaded could have been reached by a lay person standing on the footpath.
He also said that because the CTV building was able to withstand the 7.1 magnitude earthquake in September 2010, it did adhere to the building codes of the time.
But he said after the September quake it should have been red-stickered and all buildings in the city should have been treated as guilty until proven innocent.