The Opera House in Manners St may have to close for earthquake strengthening. It has been found to be below 34 per cent of the building code.
Wellington City Council is seeking reports from structural engineers about options for strengthening the heritage-listed building.
Council seismic assessments manager Steve Cody said it was likely the Opera House would have to close while work was completed.
Nothing definite about strengthening would be known until engineers' reports were received later this year.
He said the Opera House might have been declared earthquake- prone for several reasons including its age, unreinforced masonry walls, inadequate bracing because of the large open spaces within the building, and the ground conditions.
"There is nothing wrong with the building, but it is 100 years old and does need strengthening to bring it up to 21st century building standards," Mr Cody said.
"Our engineers have determined the building is less than 34 per cent of the new building standard.
"Buildings of the vintage of the Opera House were built to a structural standard different to the standard we now use.
"We obviously now know that buildings built to earlier standards do not perform as well in an earthquake."
Mr Cody said the Opera House's classification as quake-prone would not affect the day-to-day use of the building and there were no safety concerns.
"These issues will only possibly become evident in an earthquake.
"Even then the building's performance will be dictated by the level or amount of shaking, as well as the direction of the quake," he said. "It is made clear to organisations seeking to book the Opera House that it is on the council's list of quake-prone buildings.
"Section 124 yellow notices are also on display in the foyer of the building."
The council has included a contingency in the 2012 to 2022 Long Term Plan for the strengthening of the Opera House.
It will not know the cost or when the work will be completed until engineers' reports are finished.
ABOUT THE OPERA HOUSE
The Wellington Opera House was designed by Australian architect William Pitt.
It was initially known as the Grand Opera House. Construction began in 1911. Opening day was Easter Saturday, 1914.
It was restored in 1977 by the State Insurance company. It has a bigger stage than the Sydney Opera House.
- The Wellingtonian