More than 60 kg of explosives will be used for the first demolition of a building by implosion in Christchurch since the February 2011 earthquake.
The 63 kg of explosives will be placed in the 14-storey Radio Network House on Worcester Street when demolition begins on 5 August.
Ceres New Zealand will carry out the demolition along with an American-based company, Control Demolition.
Ceres recovery manager Bill Johnson says small explosives will be placed under the building's support columns, with gravity completing the job by pulling the building down.
He says once the explosive charges are placed, the demolition is expected to take about 7.7 seconds.
Workers have already been removing cladding from the southern façade.