A contract to fix the rotting Scott building at Middlemore Hospital, signed with the original builder, intends to use a recladding method the DHB called "both testing and risky".
Scott building will have its outside cladding and any bad framing replaced while patients remain inside, in its 11 wards and coronary care unit.
"The re-cladding is intended to take place while the building continues to function as a hospital for acutely unwell patients," the acting chief executive Dr Gloria Johnson said today.
Hawkins would use a breathable building wrap and a laminate cladding product from Austria on the Scott building.
Patients would be protected throughout the build, Dr Johnson said, with an Infection Control team on hand and barriers to keep people clear.
In the meantime, "while interior walls and exterior cladding is intact, there is no risk of mould affecting patients, staff or the public", she said.
Dr Johnson had previously told RNZ that demolishing the many defective buildings might be more cost effective than repairing them.
Today, the board's statement said the works "are in many ways unique".
However, in a confidential briefing paper a fortnight ago, Counties Manukau health board said there was "some confidence" in the approach but it "essentially remains untested in a wider scale".
It had found only two similar types of approach used before anywhere in the world, it said.
It also said the success of this approach would "have a huge bearing on how the other buildings will be remedied".
The DHB's former facilities manager Greg Simpson also told RNZ the approach had never been used anywhere in the world.
It comes six years after the leaks were found and a year after the DHB reached an out-of-court settlement with builder Hawkins over what the health board called "shortfalls" in the original construction of the Scott building.
Hawkins, which was bought last year by Downer in Australia, was also the firm awarded the new recladding contract, for an estimated cost of $27.5 million.
National Party leader Simon Bridges said Middlemore Hospital must be fixed as quickly as possible now the full extent of the problems was known.
The former government and health minister were not aware of how bad a condition the buildings were in, because the hospital failed to tell them, Mr Bridges said. He said now the truth was out, the new government must fix it as quickly as it could.
The government agreed to provide $11.5m last month, the week before RNZ broke the story of the hospital. There is another another six months of design work ahead, then almost two years of actual construction.
Terry Buchan, Auckland Regional Manager for Hawkins said Hawkins had "a longstanding relationship with the DHB".
"And our commitment is to helping the community in its drive for better health and wellbeing."
Hawkins and the board had worked hard on the Scott building method and had run trials using it, he said.
At least 10 other buildings run by the board at Middlemore, Manukau and Ōtara - are red- or orange-zoned by the DHB for multiple leaking, asbestos or seismic problems.
Few safety measures are in place at the moment, despite an independent surveyor recommending barriers now outside to guard against cladding falling off, and wall monitoring to spot any toxic mould breaking through the plaster from inside the wall cavity.
Some asbestos monitoring is going on in the older Galbraith building, where the health board has admitted some staff "may" have been exposed.
Panels on the KidzFirst and McIndoe buildings were also being rechecked, Dr Johnson said.