The Wellington City Council will have to come up with millions of dollars to strengthen some of its landmark buildings - and so will the owners of 1200 other properties, the Dominion Post reports.

After assessing one-third of the 3800 buildings identified two years ago as failing to meet earthquake-strengthening standards, the council is now looking at its own liability.

That will mean millions of dollars may need to be found to strengthen buildings such as Wellington Town Hall, St James Theatre, the Opera House, the Embassy Theatre and the City Gallery - a cost for which the council has not budgeted.

The council will decide on Friday whether to spend an extra $1.1 million to strengthen the City Gallery, which could be closed for up to nine months.

The other buildings were all strengthened during the past 20 years but it is not known if they measure up to the tough new building requirements the Government introduced in 2004.

Council spokesman Richard MacLean said the buildings might "have to be tweaked or work may have to be started from scratch".

The council's urban development and transport portfolio leader, Andy Foster, said it would be important to protect "heritage and amenity" factors in the buildings.

Other at-risk properties could include council-owned buildings on the waterfront, the Municipal Office Building, Wellington Railway Station, buildings at Victoria University, and some buildings government departments use.

All those found to be at risk were constructed before 1976.

Owners are liable for the cost of strengthening buildings, which must meet 33 per cent of the minimum building standards required for a new building. The costs to owners had not been robustly tested but were expected to be significant.