Hawkins Construction's $80 million upgrade of Auckland's Aotea Square is under way.
The project is one of the biggest local government jobs in the country and involves Civic carpark repairs worth $45 million, a $10 million Aotea Centre facade upgrade and $26 million for Aotea Square streetscaping.
The carpark roof, which runs under the square, had structural damage and is being strengthened and waterproofed. Work started on the project late last year and is due to finish next October.
Public access has been barred to most of the area and a crane is on-site.
Auckland City Council said changes to the wider area would be a big improvement.
"The redevelopment will restore the square to its former status as the city's leading public open space and events venue that caters to young and old, and to all interests, activities and tastes. It will be able to host major big screen events, music concerts and cultural festivals that can draw crowds of up to 20,000 people," it said.
"The initial focus is on repairing and strengthening the Civic carpark roof. The process entails layering a new roof over the existing one. Construction is under way on stage one of the project which is the hoarded area at the southern end of the square.
All landscaping has been removed, excavations have been carried out and reinforcement, concreting and waterproofing will follow," the council said.
The Grey's Ave vehicle entrance to the underground carpark was closed in November and would remain shut for about six months.
The square, flanked by the historic Auckland Town Hall, opened in 1979, three years after the Civic underground carpark was built.
Aotea Centre opened in 1990.
The Sir Dove-Myer Robinson sculpture which greeted pedestrians entering the square from Queen St is in storage until work is finished.
Last year, Hawkins, one of New Zealand's largest building firms, also started work on a controversial multi-million dollar project to restore, develop and expand the Auckland Art Gallery. That project would increase exhibition space by 50 per cent and ensure the gallery links into neighbouring Albert Park.
Hawkins said this was a complicated project which the firm won because of its experience in heritage work. A key component of the project is the restoration and upgrade of the original 1887 and 1916 heritage buildings, the builders said.
Chris Hunter, Hawkins' chief executive, said this year would be challenging but his firm was better placed than most to handle the changes.
Other big jobs for Hawkins include Charter House in the Britomart, Auckland International Airport and Mighty River Power's Kawerau geothermal power station.