The royal commission's report on the collapse of the CTV building during the February 2011 Christchurch earthquake has been handed to the Government.
The collapse accounted for 115 of the 185 deaths caused by the quake.
The report on its structure and why it collapsed is the third and final part of the commission's inquiry.
Attorney-General Chris Finlayson says ministers will consider the report and release it "in due course" with the Government's response.
It also deals with the roles and responsibilities within the building sector for assessing buildings after earthquakes, the training of civil engineers, and the organisation and regulation of the engineering profession.