72 | TIMBER INDUSTRY Dunning Thornton T T Hugh de Lacy Timber a key part of construction mix The eight-storey Tauranga City Council eco-building - the building uses engineered timber in place of concrete and steel elements for its entire superstructure of beams, columns and slabs, which are all made from LVL, CLT and glulam. Image: Jensens Fabricators. “Our focus is on the right mix of materials that ensures the highest construction quality at the lowest cost.” The future of timber in buildings, especially high-rise ones, lies in being part of a mix where concrete offers the inground durability, steel the seismic resilience and timber its speedy construction and fire rating, according to Chris Speed, a director of the Wellington structural engineering consultancy, Dunning Thornton. “The notion of large buildings being built entirely of wood is giving way to an economic mix of materials because of complications and costs arising from timber-only systems,” Chris says. “There are two key elements in mass timber construction, the first being Engineered Timber, where small solid timber sections or veneers are laminated to improve strength and stiffness, and Cross Laminated Timber (CLT) floor and wall panels which are brought on-site ready to install, allowing floors to be built quickly. “Trying to get timber to do everything in larger buildings and in areas with higher seismic requirements has often led down a path to difficulties in detailing and construction that added cost and time to projects.” “Our focus is on the right mix of materials that ensures the highest construction quality at the lowest cost,” he adds. That said, Dunning Thornton has been involved in a succession of timber-dominated engineering projects, including the largest mass timber office multi-storey in the country, built with an eye to minimising the carbon footprint. Officially opened in June last year for the Tauranga City Council, the eight-storey eco-building on Devonport Road now houses its thousand-or-so staff assembled under the same roof for the first time since 2014. The council is leasing the building back from property developer Willis Bond which bought the land from the council in 2021 for $8.5m. Built by LT McGuiness from a Warren and Mahoney plan with Dunning Thornton delivering structural engineering services, the building uses engineered timber in place of concrete and steel elements for its entire superstructure of beams, columns and slabs, which are all made from LVL, CLT and glulam. Steel was used for the lateral bracing to provide a highly resilient and proven approach to seismic risks, but the building generates only half the carbon release of a traditional steel and concrete office block, and it incorporates a façade and building services design that delivers a 65% reduction in energy consumption. Other mass timber structures that Dunning Thornton has been involved in include the Air New Zealand maintenance hangar at Auckland International Airport, Scion Research’s offices in Rotorua, and the new Fisher and Paykel homeware offices under construction in Auckland. Dunning Thornton will next year be celebrating its first 40 years since the firm was founded by Cris Dunning and Adam Thornton. Today the company is run by Alistair Cattanach, Ryan Clarke and Chris Speed and has a staff of 25. Its specialties include base isolation, seismic design, multi-level construction for the commercial, retail, residential and public sectors, as well as seismic assessment and strengthening. It has also established a reputation for itself in heritage restoration and seismic retrofit, as well as large building relocation on sites throughout the country. Other mass timber structures that Dunning Thornton has been involved in include the Air New Zealand maintenance hangar at Auckland International Airport. Image: Studio Pacific Nelson Pine Industries Ltd Proud to work alongside Dunning Thornton Ltd to provide cu�ng edge Mass Timber LVL Buildings across New Zealand 07 575 6080 31 Te Maire Street, Mount Maunganui www.jensensteel.co.nz Jensen Steel are proud to have worked alongside Dunning Thornton on the Tauranga City Council CBD Development Projects
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