More than 900 door frames have to be ripped out at the new Perth Children's Hospital as they may not comply with Australian fire standards, with Health Minister John Day blaming its builder John Holland.

Mr Day said the builder would wear the cost of replacing the 935 door frames.

The Chinese-owned company would have to work hard to meet the mid-year hand-over date after previously installing 450m of faulty water pipes.

“What I’m advised at present is it should not delay the opening of the hospital,” Mr Day told reporters.

“It is the responsibility of the builder to replace them and they are taking steps to do that.

“We would much prefer that the builder gets it right and does things on time. Now that has not been the case to this point completely.

“It would have been better if this was picked up earlier.”

The state government expects the $1.2 billion hospital will open to patients before the end of the year.

Hand-over was originally due in late 2015 but John Holland fell behind schedule.

Opposition treasury spokesman Ben Wyatt said he wasn’t confident the opening date target would be met, considering the previous delay.

“I’m not one to accept the argument that the minister simply pushes responsibility down and waits to cut a ribbon,” Mr Wyatt said.

The Nedlands facility will replace the ageing Princess Margaret Hospital for Children.