An engineering chief and an Auckland Council official have challenged claims there are widespread defects in major New Zealand buildings.

They have also called for hard evidence of structural steel being pulled from concrete before it set.

Hamish McKenzie, Structural Engineering Society of NZ president, dubbed as "hearsay" claims of shoddy work on the buildings and Ian McCormick, the council's consents manager, said his entity was unaware of any such practices.

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"I am not aware this is happening and we don't have any evidence," McKenzie said of the steel-pulling allegations.

"There's a lot of hearsay about quality issues but a lack of hard data that captures holistic quality insights across the construction sector and uses this information to inform focus areas for improvement," McKenzie said.

He was responding to media report of claims that new imaging technology revealed hundreds of major buildings nationally have defective or missing concrete or reinforcing steel.

Concrete investigators say their scanning shows many buildings have not been constructed according to the plans and one report said they were "astounded" and "appalled", Jane Roach-Gray of Wellington company Concrete Structure Investigations said.

McKenzie called for more information about the claims of poor-quality work.

"It's really important that poor quality construction work is uncovered and it's great to see new technology being used to help with this. These kinds of investigations are often carried out when there's uncertainty about what a drawing shows or whether the drawing matches what's been constructed. They're typically carried out where doubt already exists," he said.

Engineers were alert to construction quality issues when they carried out earthquake assessments on buildings, McKenzie said.

Under seismic assessment guidelines out last year, the society advised engineers that if they were assessing a building with certain features, they should consider whether those were constructed as designed, he said.

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"If an engineer wasn't sure, then they should do some investigation to confirm this, as part of their assessment. But this is just one aspect of a building that should be considered in the context of a whole assessment," McKenzie said.

McCormick said inspectors checked reinforcing steel before a concrete pour in small developments.

"In large scale developments, this is typically performed by engineers as part of a comprehensive quality assurance plan. This has been the case in large-scale construction going back to the 1980's," he said.

The council was not aware of the alleged industry practice to discard reinforcing steel and leaving it in 'skip bins.'

"We would be interested in talking to industry participants who suggest this may be happening," McCormick said.