Building owners across the country are being put on notice by a study into building collapses during February's Christchurch earthquake.

Among the recommendations coming out of the investigation is a call for councils to actively identify and deal with earthquake prone buildings, and in a shorter time frame.

The panel investigating the building collapses is also suggesting local councils be given the power to require earthquake strengthening when a building is significantly altered or when occupancy levels are significantly increased.

The recommendations are in the Department of Building and Housing report on the investigation into three large multi-storey Christchurch buildings – Pyne Gould Corporation, Forsyth Barr and Hotel Grand Chancellor.

Conducted by leading New Zealand engineering consultants with the findings peer reviewed by a panel that includes experts with international experience and standing, its recommendations include a number of changes to improve building standards and best practice.

The panel seeks to improve public awareness of the potential danger represented by older buildings that do not meet current design requirements.

It is also considering changes to the law covering earthquake-prone buildings, which are prompted by the collapse of the Pyne Gould building which was not regarded as earthquake prone.

The safety of stairs is also of serious concern. A practice advisory notice has been issued as a result of an engineer's report on the collapse stairs in the Forsyth Barr building.

The building was designed in 1988. Two flights of stairs collapsed in February's earthquake. The main stairs collapsed from Level 15 down, the other flight collapsed from level 13.

In modern flexible buildings, stair supports are designed to slide horizontally in an earthquake.

The space provided to allow for this movement is known as the ‘seismic gap'.

It stops the stair from stiffening the structure, and the stair unit from being compressed and falling off its supports.

The seismic gap in the Forsyth Barr building's drawings met the design requirements of the 1980s. It would not satisfy current Building Code requirements.

The lower support on which the stair slides couldn't accommodate the movement in the 22 February 2011 aftershock. Some gaps may have been less than specified or had debris or mortar in them.

Calculations of movement indicate that if the gaps had been full size or free of debris, the stairs would still have fallen off their supports.

The Department of Building and Housing considers it imperative that the circumstances of the Christchurch building failures are fully understood and the implications for similar buildings around New Zealand examined and acted upon, says Deputy Chief Executive Building Quality, David Kelly.

The recorded ground accelerations in the 22 February earthquake were much greater than those in the 4 September 2010 earthquake, says David.

Peak vertical accelerations in the Port Hills were among the highest ever recorded anywhere in the world.

The PGC, Forsyth Barr and Hotel Grand Chancellor buildings failed mainly because the February 22 quake was extremely violent and, when they were built, design requirements were not as rigorous as they are now.

'In the case of the PGC building, where there was tragic loss of life, the shaking was much more intense than the building was designed for when it was built in 1966,' says David.

'The building lacked resilience and the ability to move and respond without losing strength.

'Based on the findings, the expert panel has made a number of recommendations to improve building standards and best practice.

'The department is taking action on all the recommendations with immediate focus on the panel's priority recommendations.”

Tauranga City Council encourages all Tauranga owners of multi-storey commercial buildings to have the stairs checked by a structural engineer.

The council will be writing to building owners over the next few weeks to reinforce the recommendation.

The practice advisory doesn't change the current earthquake prone building assessment process. If a building is deemed earthquake prone stairs will need to be looked at as part of the remediation.

Building owners need to demonstrate that this has occurred before the building is taken off the earthquake prone building register.