A gutter full of snow and hail caused water to overflow down a section of the New Zealand Historic Places Trust category 1 historic building, including its proscenium arch.
Regent Theatre technical manager Nelson Miles said it was fortunate the irreplaceable ornate plasterwork had been recently sealed and painted, "otherwise we would have lost quite a bit".
It was also fortunate water did not affect the electrical cables under the stage, he said.
The gutter was between the flytower and the auditorium, in an area not part of the theatre's multimillion dollar redevelopment, which was completed last year.
Water began to drip on to the stage after the curtain call of the Fairfield School production on Tuesday night and dozens of buckets and large containers were used to collect the unwanted water.
Because of safety concerns, a rehearsal and last night's production by Andersons Bay School were postponed, but rehearsals for an Indian cultural evening were expected to be held today.
Amalgamated Builders Ltd contractors assessed the damage yesterday and were constructing snow boards, designed to prevent snow going in the gutter.
The gutter would also be replaced, along with a section of roof. No estimates were yet available but work could be completed next week.
"The work will take away the possibility of that kind of disaster happening again," Mr Miles said.
