All owners of multi-storey buildings throughout New Zealand will have to check their stairwells can withstand earthquakes and reinforce them if they can't.
The Department of Building and Housing is issuing the directive after releasing a report into what caused the collapse of three buildings in the devastating Christchurch earthquake on 22 February.
An expert panel employed by the department has been investigating the collapse of the Pyne Gould Guinness (PGC) building which killed 18 people, as well as structural failures in the Forsyth Barr and Hotel Grand Chancellor buildings.
The department's deputy chief executive, David Kelly, says he has advised local authorities throughout New Zealand to alert building owners and ensure that they have stairwells checked by a chartered professional engineer.
Mr Kelly says any stairwells not stable enough will have to be reinforced to the latest building code standards.
The expert panel consulted with building owners, obtained council files, original drawings and interviewed witnesses and USAR staff who helped rescue people from the buildings in February.
Panel member Richard Sharpe says the main reason the five-storey PGC building collapsed was because the ground acceleration was several times larger than the building, designed in 1963, was built to withstand.
Dr Sharpe says the core of the building collapsed above level one, the columns around the building snapped, and the connection between the floors and the walls pulled apart.
The Department of Building and Housing is working to prepare a submission on this material for the Royal Commission into the disaster which will look at why certain buildings collapsed.
The report and presentation of information was shown to families of those killed in the PGC building's collapse on Friday before being released to media.
A report on the collapse of the CTV building, in which 115 people died, is still being compiled. David Kelly says this investigation is extremely complex and will not be completed until late this year or early in 2012.