Winner ready for the big one

This Issue This is a part of the Commercial buildings feature

By - , Build 173

The PwC Centre, the big winner in the 2019 New Zealand Commercial Project Awards, is ready for Wellington’s next big shake. The building includes continuous flight augured piles – a first in New Zealand.

THE PWC CENTRE recently won the Registered Master Builders Supreme Award in the New Zealand Commercial Property Awards as well as the National category, Gold and Value category (over $15 million) awards.

Located on Wellington’s waterfront

5 minutes’ walk from the central railway station, the base-isolated PwC Centre is built on reclaimed land. There is an underground car park for tenants, food and retail spaces on the ground floor and four floors of offices above. Wellingtonians can use a public walkway through the PwC Centre to get to the waterfront from Waterloo Quay.

Seismic resilience important in design

Earthquakes pose a significant risk in Wellington even when they are centred some distance away. The epicentre of the 2016 Kaikōura quake was 200 km south, yet still caused over $1 billion of damage in the capital. Some recently built commercial buildings not far from the new PwC Centre could not be reoccupied after the Kaikōura event and had to be demolished.

With the PwC Centre, the intention is not merely that tenants can evacuate safely, but that they can quickly get back to work in the building afterwards. The design achieves 180% of the new building standard (NBS). (The % NBS figure is a measure of a building’s performance over a range of earthquakes in terms of protecting life.)

Jeff McHardy, Project Manager on the PwC Centre for builders LT McGuinness, says Wellington commercial property tenants are a lot more savvy after the recent Kaikōura event. Blue chip companies in particular are looking for good earthquake resilience in buildings. ‘It is expensive for them to be out of a building for many months while ceilings and services are repaired.’

CFA piling first for local commercial property

The PwC Centre is supported on over 1,200 continuous flight augured (CFA) piles. While this method has been used on civil projects, this is the first time it has been used in this way in New Zealand commercial property.

With CFA piling, the piles are cast in situ, especially suitable for sites like this Wellington one, where there is unstable or saturated ground. An auger with a hollow stem is drilled into the ground to the required depth. As the auger is removed and ground material extracted, concrete is pumped down the hollow shaft under pressure, forming the pile – there is never an empty hole. The steel reinforcing is then placed in the wet concrete pile.

Apart from its suitability for this type of ground, CFA piling has other benefits. It produces little vibration and noise nuisance compared to some other foundation options – a significant advantage in a busy built-up area like the Wellington waterfront.

The first group of piles around the building perimeter, 8–10 m deep, effectively created a waterproof bathtub wall. Water was pumped out, and the PwC Centre’s underground basement below the waterline was constructed. Further CFA piling was undertaken at the basement level to form underground cellular grids. This was used to mitigate liquefaction, control the lateral spread and provide a cost-effective foundation for the superstructure.

Isolators and non-structural elements

Construction above the piles included 33 lead rubber bearing base isolators and 31 slider isolators.

Seismic resilience goes beyond the main structure itself – services and non-structural elements such as waste runs and ceilings can cope with significant earthquake movement.

Above ground, a striking feature of the building is its cantilevered southern end. The exposed underside of level 3 is clad with cedar.

The four office levels in the building have floor plates of over 2,000 m2. Extensive glazing overlooks the harbour and city and maximises natural light.

A challenging build

There was a 2-year building programme, but Project Manager Jeff McHardy says the timeframe was tight from day 1. ‘The building almost has two sets of foundations, and the first 13 of the 24 months of construction were taken up with foundation work.’ The building work went quickly after that and was completed in May 2018.

Good communication, good teamwork and a project-wide commitment to quality meant the timeframes were met without compromise. Athfield Architects provided the design work, Dunning Thornton Consultants the engineering and Brian Perry Civil completed the CFA piles.

In their comments about the building, the Award judges said: ‘LT McGuinness delivered a stunning, well balanced, award-winning 5-storey building at a prime Wellington waterfront location.

‘This teamwork particularly impressed ... It demonstrated a great level of trust, collaboration and a high standard of workmanship across all trades. The completed building was a credit to all involved and shows how a team approach will always provide a winning result.’

5-star Green Star design rating

The PwC Centre has a certified 5-star Green Star design rating. The Green Star rating takes account of energy, water, materials, indoor environment quality, transport, land use and ecology, management, emissions and innovation. The PwC Centre building was developed by Willis Bond & Co.

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