A construction company has been ordered to pay $13.4 million to fix a raft of errors at a leaky, damp, and rotting secondary school in Auckland.

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Botany Downs Secondary College in Auckland was built in stages by Hawkins in the 2000s, opening in 2004.

It has almost 2000 pupils and more than 100 teachers.

H Construction North Island - formerly called Hawkins Construction North Island - was liable to pay the Ministry of Education the sum of $13.4m for the shoddy construction, a High Court judgement said.

The judgment said the ministry and the school board claimed nine buildings leaked and the estimated repair bill was $17m. They claimed roofs were badly built, parts of the buildings were rotting, and fungus was present.

They also claimed there was a badly built gym floor and there were regular problems with gutters, flashing, eaves, pop-up roofing and inadequate ground clearance.

Hawkins accepted there was poor workmanship but submitted the college was up to code. The company's lawyer claimed water-blasting by the school may have caused the damage but the court described this claim as "unsatisfactory" and no water-blaster was called to testify.

McConnell Group, which has since bought Hawkins, said it was surprised by the judgment and would reflect on it before commenting further.

Justice Mathew Downs said the repairs were likely to take about two years and require temporary accommodation while the buildings were quarantined during work.

"The roofs leak because they suffer a host of construction defects, including missing fixings and poorly formed penetrations. Nothing the plaintiffs did or did not do causes them to leak," he said.

"The sum is not small, but Hawkins was paid approximately $28 million to build the school; pupils and teachers have not had the benefit of healthy code-compliant buildings for eight years, and the award reflects the amount necessary to repair the school, not more."

College principal Karen Brinsden told the court about "constant" and "extensive leaking", with water regularly coming through roofs. Buckets were used to collect rainwater in classrooms and there were regular leaks and flooding, the judgment said.

The ministry, Hawkins, and the school have been contacted for comment.