Several North Island DHB facilities are being described as "medieval."

A new report's found around one-fifth of Auckland and Northland hospital facilities, including Starship Children's Hospital, are beyond their life expectancy or "not fit for purpose".

While it doesn't detail specific problems with the buildings, health unions have flagged leaks, mould, size and upkeep of the rooms as possible issues.

Resident Doctors' Association national secretary Dr Deborah Powell says one lab at the Whangarei Hospital is like something from the dark ages.

She says the lab has been on the books for a "desperately needed" upgrade for more than a decade but nothing's being done.