Seven thousand commercial and public building owners have been asked to supply Cera with engineering reports as part of its safety stocktake of Christchurch buildings.
Between September and mid-February, the Canterbury Earthquake Recovery Authority had sent 561 requests for detailed engineering structural assessments, with most going to owners of unoccupied buildings within the inner city.
However, at the weekend, Cera sent out engineering assessment requests to the owners of the remaining 7000 buildings on its list, a spokeswoman said.
Some of the building owners, whose buildings have not been subject to section 51 Cera inspections, were sent introductory letters.
These encouraged them to gather structural information about their building so they could quickly respond when asked in the future, the spokeswoman said.
Most letters were specific to a particular building and asked for detailed engineering evaluations within eight weeks.
However, the timeframe was flexible as long as Cera was kept informed about the assessment, she said.
Engineering evaluations were demanded by Cera as its way of stocktaking the structural integrity of Christchurch's commercial and public buildings.
The evaluation is overseen by Cera engineers who determine whether a building is compliant with the revised Building Code.
If it does comply, Cera passes the file to the Christchurch City Council.
If not, the owner is asked to do strengthening work. In the meantime, access to the building would be restricted.
Access has been restricted to about 34 buildings after the return of 148 evaluations to Cera as at February 15.
Cera operations general manager Warwick Isaacs said previously commissioned engineering reports would be considered for detailed engineering evaluations of buildings.
Some may need reports, others would not, each building's situation would be different, he said.
Institution of Professional Engineers New Zealand chief executive Andrew Cleland said the assessments were detailed and unlike the triage checks made immediately after the earthquakes.
For many commercial buildings the assessments could cost "some thousands of dollars" each, he said.
The assessments had to be done under the Structural Engineering Society New Zealand guidelines which meant a structural engineer had to check the building's plans, make calculations and investigate where damage was suspected to have occurred.
"It's a significant amount of work. It can't just be done by a walk-through."
Cleland said Christchurch engineers were busy and the reports required by Cera would increase the workload.
The ability of engineering firms to temporarily relocate staff to Christchurch to deal with an increase in work would be limited, he said.He was uncertain how long it would take for the assessments to be completed.