This country's tallest wooden office block will have revolutionary design aspects including a rooftop device to protect the block during earthquakes, its developer says.

Sir Bob Jones, chairman of Robt. Jones Holdings, said all approvals had been granted for the block on the Leaders Building site, corner of Brandon St and Featherston St and demolition of the existing block was well advanced.

"A revolutionary device on the roof involves a large weight on rollers. In an earthquake, this will roll in an opposite direction to the shake and nullify the movement. That's the same principle of a sudden stop or crash in a car in which the driver is thrown forward," Jones said.

His comments follow a call last week for a tall Auckland tower to show what can be done, construction of a Sydney wood office block and plans for a 70-level wood tower in Japan.

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"These have huge advantages over the conventional steel as they won't buckle in an earthquake, which single factor has been the reason for the recent demolition of several new buildings in the city," he said.

The 12-storey 52m tall office block made from laminated timber columns and beams which perform better in earthquakes than steel or reinforced concrete because they are less likely to buckle, Jones said.

"The internal removal of asbestos of the existing building took three to four months and finished a month back. Currently the internal demolition is going on and will be followed by the total demolition which is apparently quite quick," he said.

Construction would start in August and finish around March next year.

Jones said he was inspired to build the wood tower after the topic rose to prominence last year and was being widely discussed.

"I rang the architects. 'Have you read this stuff?' I asked. I received a cautious yes. 'Then why don't we do this?' I asked," Jones said.

"I'm slightly embarrassed by this as people will expect to sort of see wood. They won't. The wood component is solely in the critical engineering elements, specifically laminated timber columns and beams.

On the issue fear about wood buildings burning down Jones said: "Office buildings' fires are rare, however, in such an event, again steel buckles while laminated timber can't burn and merely gets singed."

Sourcing a construction company was a challenge, he said.

"No builder - or at least the larger firms - will give a fixed price," Jones said, referring to construction sector losses. "They will give a base sort-of fixed price with a cost-plus for various elements. We're happy about that as we have on our staff a seasoned veteran construction supervisor."

Robt. Jones Holdings was formed in 1961 and says it "is now New Zealand's largest private CBD office building owner, and specifically, the largest in Auckland and Wellington with 25 buildings in total", 800 tenants and a $1.5b portfolio of properties here and in Australia.