Hutt Hospital has 10kg ceiling tiles which could put people at risk of serious injury in a major earthquake.
The tiles are in corridors and foyers in a block housing the maternity, medical, coronary care and children's wards, but not in any patients' bedrooms.
Documents released under the Official Information Act show that in October an engineer scored the hospital's eight-story Heretaunga Block a three out of 10 for how its cables, pipes and sprinklers are braced to withstand a quake.
The heavy tiles are spread out over 3800 square metres.
"It's clearly a risk and one we're taking very seriously," said chief executive Ashley Bloomfield.
He said that in the Kaikōura earthquake of November 2016, only a handful of tiles fell down but conceded that in a different type of shake it could be worse.
The near-new $80 million Emergency Department, ICU and operating theatres had no ceiling issues and were rated highly, he said.
In their October report, engineers Advanced Building Services said there were deficiencies and "as this building includes multiple theatres, we believe the seismic bracing of all services needs to be fully robust to ensure that there is a high chance that all the services will survive a substantial event".
A consultant told RNZ that other hospitals across the country have similar unsafe ceilings.
"A lot of the ceiling tiles that we know of in hospitals are the old decramastic, heavy, plaster tiles," said Hedda Oosterhoff, national architectural manager of Wellington company T&R Interior Systems.
"So we're actually working with a number around New Zealand - having preliminary discussions with one on the West Coast, Wellington's actively changing theirs [ceiling] at the moment."
The threat was from the accelerating fall from height of a 10kg tile, and its sharp edges.
"Christchurch [2011 quake] was the first people had their eyes opened to progressive collapse where part of the ceiling fails and it drags the whole rest of it down," said Ms Oosterhoff.
"We saw a lot of examples of ceilings where half of it was still on the ceiling and the other half was lying on the ground."
Six years on, most hospitals have not identified or fixed their substandard ceilings or seismic restraints.
Hutt Valley DHB to replace tiles
The Hutt Valley District Health Board called in engineers in October to inspect all its restraints.
The engineers found a host of shortcomings, including water tanks and control cabinets for the passenger lifts not braced, and electrical cables that posed a risk to sprinklers and needed urgent fixing.
There were also issues with bracing of essential water piping and drainage in the Heretaunga block, which could swing in a quake causing damage.
Hutt Valley, Capital & Coast, and Wairarapa district health boards briefed Civil Defence last month on their non-structural restraints following RNZ inquiries in July.
Wairarapa said it had lightweight ceilings in its main hospital in Masterton, and had an engineer now checking all its seismic restraints. Capital & Coast DHB has yet to provide information to RNZ under the Official information Act.
Capital & Coast and Hutt Valley DHBs have found a lightweight ceiling tile to use and work will start early next year. Hutt Valley DHB has recently sorted a back-up electricity supply for after a quake, and will shortly boost its emergency drinking water supply from less than one day to the seven days required under resilience rules.
Read the engineers' report on seismic restraints at Hutt Valley DHB here.
Hutt Valley DHB engineering assessment scores on non-structural seismic restraints:
(a score of 10 would indicate full compliance)
- Emergency Department and Theatre Block: 8 out of 10
- Clock Tower Block: 5 out of 10
- Heretaunga Block (includes maternity, medical, coronary care and children's wards): 3 out of 10