Watch $850m project: preparing for NZ's biggest commercial development

Demolition of Auckland's Downtown shopping centre is finishing and earthworks are beginning for the $850 million Commercial Bay office/shopping/dining precinct in the CBD.

In a video just released, Precinct Properties chief executive Scott Pritchard talks of the huge challenge demolishing the 70-shop mall at the end of Queen St and the next phase of work.

"To achieve this is a major milestone for the project," Pritchard said of the demolition job.

Fletcher Construction won the contract to build the 39-level PwC waterfront tower. Twin tunnels for the $3 billion-plus City Rail Link will run beneath it, turning from Britomart up Albert St.

Zurich House or 21 Queen St stands in the centre of the site.

Ward Demolition had brought the centre down, Pritchard said, and materials from much of the old structure had been recycled.

"If you had of stood here and watched this building come down for the last four or five months, you would have seen them in almost every aspect pick out the steel, pick out the concrete. Then each material has been recycled," Pritchard said.

The next phase would be putting structure in the ground, then excavation. About 600 piles would be driven into the ground and about 200 of those were already in place, he said.

Commercial Bay will be a new office tower with a retail offering which would be transformational for the city centre, with about 100 shops but also bars, restaurants and cafes, Pritchard said.

In a controversial move, Auckland Council is selling Precinct part of Queen Elizabeth Square for the new development. Precinct also plans to develop a new pedestrian lane way from the square through to Lower Albert St.