Ashburton hospital's operating theatre is closed, because engineers have assessed the building as an earthquake risk.
Canterbury District Health Board chief executive David Meates met theatre staff on Tuesday morning to tell them about the closure.
Thirteen patients are affected on Tuesday. Decisions will be made over the next several days about where patients will have their surgery in the short-term.
Mr Meates says the board is waiting for engineering assessments on the other buildings on the Ashburton site.
Since the first earthquake on 4 September 2010, more than 7500 hospital rooms in Canterbury have been damaged.
The board's repair bill, originally estimated to be about $70 million, is expected to rise.