BOWEN STATE BUILDING

PROJECT TYPE: COMMERCIAL BUILDINGS

USE: OFFICE

LOCATION: BOWEN STREET, WELLINGTON

CLIENT: PRECINCT PROPERTIES; NZ DEFENCE FORCE

ARCHITECTS: WARREN AND MAHONEY; PLANET DESIGN

PROJECT TIMEFRAME: 2016—2019

The Bowen State Building (BSB) is the nerve centre of the country’s security and defence systems. Its primary tenant, the NZ Defence Force, moved in three years after its central headquarters in nearby Aitken Street was destroyed in the 2016 earthquake. BSB’s seismic capacity rating today is 100%.

Built by the Ministry of Works in the 1960s, BSB had become rundown architecturally after nearly 50 years of constant use. However, the structure was suitable for a seismic upgrade.

In 2016, demolition stripped the 10-level building back to a concrete shell. The lower six floors were extended to the north and east in an annex to provide an additional 8500m2 and a total floor space of 34,250m2.

Four x 25m deep new 1500dia board piles with 3.6m wide bells were required to hold and anchor two new 10-storey shear walls that give the building stability. In a technique untested before in Wellington on this scale, the four belled piles were linked as two sets by two massive 220m3 transfer beams.

It was critical to correctly sequence the three main elements: cutting the two existing central core walls into three disjointed sections and installing 36 new bearing plates; building the two new shear walls; and adding the annex wings.

The southern shear wall provides both structural integrity and an architectural feature. A fibreglass mould made specifically to match the contour of the façade also resulted in exceptional high-finish concrete. BSB’s new lobby and ground-floor retail and hospitality spaces look out on Parliament’s sculpture garden.

It was a huge job, involving the pouring of 2631m3 of concrete, the largest ever undertaken by LT McGuinness. One single pour was 220m3. At the job’s peak, 300 staff and subcontractors were on site.

For much of the three-year project, LT McGuinness was also working on the adjacent Charles Fergusson Tower (CFT) as part of a wider Bowen campus development. Two new office blocks in Bowen Street, in addition to the BSB and CFT rebuilds, will complete a complex worth $350 million in total. Ultimately around 5000 office workers will occupy the campus.