Located in Tāmaki Makaurau Auckland, the $36 million Henderson Service Centre & Transport Interchange (formerly Waitakere Civic Centre) was designed to optimise the area’s sustainable design objectives by integrating new energy efficient Auckland Council (formerly Waitakere City Council) facilities to serve as a green community and transportation hub.

“Designed by Architectus in conjunction with Athfield Architects and sited adjacent to the North Auckland Rail Line, the new Civic Centre comprises three main elements – the Civic Wing containing the Council Chamber, Councillor’s facilities and the Directorate; the Administration Wing containing public interface facilities and open-plan office space for council staff and the Link element, which forms the main public access and pedestrian connection to the new rail station and local business district.” ~ ArchDaily

Weight being a critical element of the green roof concept, much research into the most suitable substrate has taken place, including field trials on a range of mixes – pumice, vermiculite, and composts – on the Waitakere Central Civic Centre roof. Over the entire roof surface, an Atlantis recycled plastic drainage cell layer has been installed followed by a Geotextile cloth, protecting the membrane from any root damage, and allowing drainage to the roof outlets. Flo-cell 20mm & Turf Cell drainage cells were used.

Mixes were required to weigh less than 230kg per square metre at a depth of 150mm to meet the structure loading requirements of the building and allowing for plants and other materials and maintenance staff accessing the roof. Wind resistant substrates that avoid windborne debris were also a consideration. The final mix selected from these trials was expanded clay, pumice, and garden mix.

Construction and monitoring of the extensive green roof at the new Waitakere Central Civic Centre building in Henderson has been funded by Waitakere City Council to provide quantitative information to help overcome barriers to adoption of green roofs on buildings in New Zealand and to promote the use of native plant species on New Zealand green roofs.

The aim is to look down over the city in the future and see a proliferation of living roofs absorbing and slowly releasing stormwater – a network of vegetated steppingstones with native plants and insects reducing the heat and noise of the city.

Plant species chosen for use on extensive green roofs have evolved from choosing the most drought tolerant plants. Succulent sedums are often chosen as they have grown naturally on roofs and walls with little substrate and are therefore adapted to extremes and lack of moisture. Waitakere City’s aim was to find New Zealand native alternatives that will form a dense, weed-resistant cover and survive in these very droughty sites with little watering.

Waitakere City Council plan to monitor how clean the water run-off from the green roof is and compare that to a normal roof. They also monitor the success of the native plants and the habitat value of the green roof.

Henderson Service Centre (Waitakere Central Civic Centre) roof water is pumped to a roof tank to be used for flushing toilets in the buildings while rain from the civic square surface is being collected in water features and pumped back up to a main tank for reuse in these features. The main water supply for the water features come from the roof of the Civic Centre building. There are a series of rain gardens throughout the site collecting rainwater, with overflow water being collected in a main drain leading to a sand filter.

Henderson Service Centre awards include: NZIA New Zealand Architecture Award – Public Architecture 2008; NZIA Auckland Architecture Award – Public Architecture 2007; PCNZ Property Industry Excellence Award – Special Purpose Building 2007; PCNZ Property Industry Excellence Award – Urban Design 2007