Steven Joyce (left) and Nigel Morrison were at a briefing to announce the convention centre deal. Photo / Greg Bowker

The architects behind the $402 million New Zealand International Convention Centre say they have designed a three-level building with each storey double the height internally of SkyCity's existing convention centre.

Moller Architects' Gordon Moller and son Craig have been working with SkyCity Entertainment Group for some years on the $402 million development between Hobson and Nelson Sts.

"It will be the equivalent of six levels because each floor is 12m high to accommodate the international facilities," Gordon Moller said.

Both were at the briefing to announce the deal, with attendees including Economic Development Minister Steven Joyce, SkyCity chief executive Nigel Morrison, Auckland Mayor Len Brown, Auckland Council Property chief executive Doug McKay and Auckland Tourism Events and Economic Development chairman David McConnell.

Gordon Moller said internal spaces in SkyCity's existing convention centre, below its SkyCity Grand between Federal St and Albert St, is 6m high so stud heights in the new building would be double that.

Craig Moller said although the site was relatively flat, sloping only 8m from Nelson to Hobson St, designing such a big building presented some issues.

"The challenge is to connect into the street and wider Auckland and [the] light, outlook, views because that's what makes Auckland unique."

The centre's main views would be towards the north and west, particularly the harbour bridge and wider vistas towards the Waitakere Ranges, the architects said.

The practice also designed the Sky Tower and the existing SkyCity Convention Centre.

Gordon Moller said 900 carparks would be built at the new convention centre, most of them in two underground levels.

An air-bridge would be developed to span Hobson St and the architects said it would be like the Federal St air-bridges in form and appearance.

One floor would be a plenary level and another floor would be exhibition space.

SkyCity said the total completed cost of the development, including land, build, fit-out and financing costs would be more than $400 million, which will be funded from operational cash flows and committed existing and future debt facilities.

Philip King of Fletcher Building indicated that business was keen to win the work to develop the building.

"We would certainly be interested in participating in the convention centre build but that's a decision which SkyCity has to make."

Brown, who was not a party to negotiations between the Government and SkyCity, said Auckland could get up to 40 conventions a year.

He said the existing amenities meant the city missed out on a huge amount of business.

"We can't compete. We do six [conventions a year] at the moment," Brown said.

"This is the Government dealing with SkyCity and I've not been a part of it. This is a project for the country and it just happens to be in Auckland. But boy, it's a lot of jobs for people in our city, particularly the young people."

Whether SkyCity's application would be for a building which complies with planning regulations, is prohibited or discretionary is unknown but Brown said he would leave those aspects to planning chief Roger Blakeley's team.

Steven Joyce, Economic Development Minister, said a convention centre on the land would be a permitted activity.

"Auckland Council will have to go through its processes," he said.

Asked about private land involved in the deal, Joyce said TVNZ's land was in a "public" entity, with the broadcaster being a state-owned enterprise.

"We've had a conversation with the chair and they're willing to sell the property at a fair price," he said, indicating the deal was strictly on commercial terms.

Nigel Morrison, SkyCity chief executive, said an extra $10 million had been spent on land.

Last year he said $30 million had been invested acquiring a land bank opposite the main Auckland site around 101 Hobson St, beside TVNZ's national headquarters.