Opuke Thermal Pools and Spa

Entrant: 
Sheppard And Rout Architects Ltd (Architect) / Ruamoko Solutions (Structural Engineer)

Category: 
9. Hybrid building award

Photographed by: 

Jason Mann

The Opuke Thermal Pools and Spa project is an innovative new sustainable hot pools facility in Methven near Opuke (Mt Hutt). The development is an exciting all-year-round facility for the Methven area and a popular destination for Canterbury tourism market.

The building features a true hybrid of structural materials, each used to maximise their individual properties to create a stunning building and visitor experience. Precast walls are both retaining and seismic shear walls adding thermal insulation, durability and seismic resilience to the building. The feature LVL timber grid roof structure was purposely used to contrast with the concrete floor and walls, creating a beautiful union of architecture and structure. Linking the two, structural steel was used discreetly to help connect the timber and concrete, maximise the openness of the façade and to provide additional seismic connectivity across the roof.

The timber roof forms both the architecture and structure, and the effect would not have been possible without the use of engineered timber. A structural steel roof structure with faux timber cladding may have achieved a similar appearance, but without the honesty, sustainability, constructability, weight saving and cost benefits that were ultimately realised. The design featured close collaboration between Architect and Structural Engineer to overcome the engineering challenges, and to seamlessly integrate the engineered timber with the structural steelwork and concrete shear walls.

The building geometry presented one of these challenges. The wall layout and roof falls were not orthogonal to the LVL roof grid which resulted in irregular spans and support locations. Two-way action of the grid roof was provided through selected moment resisting junctions using bolted steel plates, threaded rod ties, engineered timber screws and steel rivet plates connectors. These connections provided the necessary strength and stiffness to allow for the large two-way spans, but were carefully concealed within the sections to be invisible in the finished building. Seismic design challenges from the irregular wall layout were solved by addition of concealed steel ties to transfer seismic demands from the roof to the precast concrete shear walls. A combination of hybrid connections were used to support the precast wall panels out-of-plane and to transfer seismic loads into the walls.

The prominent use of timber was a deliberate design move from the onset. Firstly, it helped meet the strong sustainability goals of the project brief by using sustainable materials. Secondly, the choice was design driven by creating an amazing customer experience befitting the high-end hot pools and exclusive luxury spa offering. To fulfil the desired visitor experience, visitors enter the building through a ‘valley’ of gabion retaining walls, precast entry walls and a ‘mountain stream’ water feature before discovering a large internal volume promoting the views to the pools and mountains beyond. The open space is characterised by the prominent timber roof structure which contrasts with the dark concrete floor and walls. With expression of the key construction materials throughout, the elegant LVL solution was a key to the success of project and it’s architecture and structure.