The architects behind three of the badly leaking buildings at Middlemore Hospital are defending their work.

Photo: RNZ / Jesse Chiang

The KidzFirst children's hospital, Manukau SuperClinic, and McIndoe Building were all designed by Chow Hill, based in Auckland and Hamilton. They were built in 1999 to 2001.

All have acute medical services in them.

The first two are particularly bad, with toxic Stachybotrus mould and brown rot in multiple places inside the walls. The framing is so wet in all three in places that moisture levels in tests hit almost 98 percent, when they should be under 18 percent.

The health board has said it was alerted to the leaks when the buildings were between 11 and 13 years old, which is outside the 10-year limit to sue contractors.

Darryl Carey is a director of Chow Hill and New Zealand Health Design Council.

"Chow Hill have provided architectural and health design services to almost all DHBs over the last 25 years and all of our projects are designed and built to the highest standards," Mr Carey said in a statement to RNZ.

"The Middlemore buildings, like the vast majority of our hospital buildings, were properly designed in accordance with the Building Code durability requirement of 50 years and were not designed for a short life."

Middlemore's facilities manager from 2008 to 2016, Greg Simpson, told RNZ he had expected the buildings to last only a relatively short life according to the way they were built and regardless of any leaking.

Chow Hill not only designed the three buildings but did construction monitoring of them.

The DHB has blamed "shortfalls" in construction in part for the buildings' failures, though it also said lax building standards at the time (1991-2004) that allowed cladding to be fixed directly to untreated timber frames were "mainly" to blame.

However, the Building Disputes Tribunal in 2015 found that the main problem was the failure to fix the cladding properly, by the builder which was Hawkins.

Hawkins settled out of court for cash to the DHB last year.

Chow Hill has also done work at Waikato and Thames hospitals, Christchurch Women's Hospital and the new Christchurch Acute Services Building which is the country's largest and most technically advanced hospital.

At the Waikato Hospital Academic Centre project, there was some roof gutter leaking that was fixed, "but this was not a 'leaky building' nor affected by cladding issues", Mr Carey said.

All Chow Hill's projects were "properly and professionally designed and documented".