Chunks of heavy ceramic tile have been falling off the Governor-General's official residence during Wellington's notorious high winds, prompting building experts to deem its roof unsafe.

Expert advice sought by officials also says Government House could suffer "significant structural damage" in an earthquake, and any deferral of a scheduled restoration project could render the building "uninhabitable, unsafe and non-compliant".

In addition to hosting members of the royal family and heads of state, the large, wooden two-storeyed house near the Basin Reserve cricket ground attracts more than 15,000 visitors a year to a range of functions, including investitures, receptions, conferences, concerts, exhibitions and community morning teas.

The Prime Minister's Department - which is responsible for the maintenance of Government House - secured more than $800,000 in last month's Budget to obtain further specialist assessments of structural and refurbishing priorities.

That work will provide the basis of a restoration project set to be approved in next year's Budget.

A spokesman for the PM's department said initial seismic testing had indicated the building's walls might have to be strengthened to bring them up to modern building standards.

The other priority was the building's red-tiled roof.

"It is not going to fall in. It's well-engineered."

However, pieces of tile had been breaking off and falling to the ground - so far without hitting anyone.

Fixing the loose tiles was difficult because of their relatively small size, and finding a solution was going to be a challenge.

The spokesman said expert assessments over the next 12 to 18 months would determine whether the building could still be used while it was being rebuilt or whether the Governor-General would have to move out.

Renovations would also have to blend in with the character of Government House as a historic building.

The house, which overlooks Newtown and covers about 4200sq m, was built between 1908 and 1910.


REGALLY APPOINTED

* The building has a grand staircase, ballroom, flag tower, 11 bedrooms and two suites.

* The residence, nearly 100 years old, also contains a wing of offices occupied by the Governor-General's staff.