Western Australia's building regulator is investigating claims of defective firewalls at the new Perth Children's Hospital, as the construction union warns that replacing them could take many months.
Building Commission director of compliance Sandy Randall said the information came from an anonymous source about the construction and inspection of firewalls at the already-delayed project.
"Building Commission inspectors are conducting a preliminary assessment of the firewalls to establish whether there is any validity to the information received," Ms Randall said.
CFMEU state secretary Mick Buchan said the complaint was detailed and he was concerned the allegations would prove accurate.
The firewalls may need to be ripped out and replaced, he said.
"The worst case scenario is it could take months and months if they do it all at once," Mr Buchan told AAP.
"They can't accept anything less than the Australian Standard."
WA Treasurer Ben Wyatt indicated to reporters he wasn't overly worried.
"I've not yet received any information that would suggest to me that the Building Commission is particularly concerned about something that no doubt, as a result of what's happening today, will get a report in due course," he said.
The main problem that continues to plague the hospital is elevated lead levels in drinking water and the opening date remains unknown.
Mr Buchan said he didn't believe the state government acted prematurely by accepting handover from the builder before the water supply was given the all clear.
He said it was a common strategy to get more hands on and take control of a project, and didn't affect warranties for defects.
