St Albans Community Centre… using wood increased seismic resilience due to the lightweight nature of the structure.
Photo: Crispin Schurr

THE New Zealand Institute of Architects works continuously to improve the quality of the country’s built environment. It stages public events to promote the awareness and importance of design … and runs a peer-reviewed awards program that sets the standards for New Zealand architecture.

The institute’s annual regional awards are currently taking place across eight constituent branches, leading to national awards, which 
are traditionally held later in the year.

Prominent among the Nelson and Marlborough entries is Waimea College (new teaching clocks) by Arthouse Architects and Sheppard & Rout Architects.

Given the school’s large catchment area and the need to cater for demand from new residential developments, the Ministry of Education commissioned an eight-classroom teaching block with a nod to the region’s extensive experience with timber construction methods.

The project features locally-sourced LVL and ply hybrid walls, timber floors and decking and often-exposed LVL beams – emphasising the structural integrity of the build.

Both the architects and builders noted the significant carbon sequestration achieved (and carbon avoidance measured) throughout the construction process.
Architect Jasper van der Lingen, a director at Sheppard & Rout, says his firm has some experience designing with engineered wood.

“For example, we completed a three-level office building in Christchurch involving an LVL structure – columns, beams and floor joists – which employed an innovative post-tensioning system to resist seismic forces,” Mr van der Lingen said.

He notes that working with engineered timber in large-scale commercial projects is still relatively new.

“Unlike steel there are no standard sizes or details which have become industry norms yet,” he said. “This tends to mean most designs are more bespoke, which can add to cost and design time.

“In addition, the capacity of the engineered timber industry is stretched at times to meet the increasing demand.”

Nevertheless, he was pleased with the speed of construction given that most of the LVL components were prefabricated off-site at nearby Nelson Pine from locally-sourced timber.

The project’s innovative LVL floor and roof panels were provided by Potius Building Systems. Structural engineer Gavin Robertson says, “they are what we call our ‘box beam’ configuration. All components work in composite, like a stressed skin panel. The sides of the box are webs, while the ply on top and LVL on the bottom act as flanges. The flooring also provides a diaphragm for wind/seismic actions.

“Fire-rated GIB ceilings provide protection to the flooring above and the sides of the boxes. The bottom portion of the box panel is exposed to the fire and protects the rest of the panel above through timber charring.”

A winner in the Canterbury region’s public architecture category is Kohinga St Albans Community Centre by Christchurch City Council. The all-timber project – which replaces a previous resource facility damaged in the 2011 earthquakes – features a large hall, several meeting rooms, and an open-plan kitchen.

The judges noted the centre’s beauty and warmth “gained throughout from the radiata cladding, spruce glulam beams, and cross laminated timber walls, ceilings and floors”.

Brent Smith, head of Vertical Delivery, says the community facility is the council’s first completed design that involves extensive use of engineered wood as both the structure and finish.

He adds that off-site prefabrication required early and extensive coordination of all aspects of design, including acoustics, fire safety and services penetrations – so engineered timber costs became comparable with other structural systems.

“Once the prefabricated timber arrived on site, the installation was seamless, which minimised crane time, and reduced overall construction time and exposure to health and safety risks.”

Mr Smith says finding a reasonably priced local supply was challenging. “In the end, it had to be imported, which had a small impact on the project’s carbon footprint.”

Overall, he believes there is much to recommend designing with engineered wood. “There was no specific fire resistance requirement due to CLT’s stable and predictable charring rate. All beams and panels have sufficient strength to resist a fire as prescribed by the building code.

“Using wood reduced the complexity and cost of the foundations; and increased seismic resilience due to the lightweight nature of the structure … negating the poor ground conditions encountered by the structural engineers.”

MAIN PIC: Waimea College… most of the LVL components were prefabricated off-site using locally-sourced timbers. Photo: Virginia Woolf