Cross-laminated timber used to be just for small buildings. That was then.
Throughout recorded history certain building materials have revolutionised the way societies have built. For the Romans it was stone. In the gothic age intricate masonry took over, before Tudor England fell in love with timber and thatch. Eventually, concrete and steel help built the first megacities in America. So what material opens up new opportunities for the post-modern world? Some say it is time for cross-laminated timber (CLT) to transform how we build.
“It’s an incredibly environmentally-friendly material,” says Phil Gardiner, managing director at Irwin Consult, Melbourne’s foremost engineering consultancy. “It’s incredibly warm, and performs well acoustically too. And apart from its technical performance, I think some people are adopting to it for the simple reason that it’s a very familiar material.”
In lay terms, consider cross-laminated timber as an elaborate form of Jenga. CLT comes in various-sized panels, made up of multiple structural lumber boards, stacked at perpendicular angles and glued together. What results is an incredibly lightweight, versatile material that gets stronger with age. It also avoids some risks commonly associated with regular timber. “The moisture content of CLT is low, which means it doesn’t twist or warp like other timbers might,” says Gardiner.
Of course timber has long been a mainstay for small-scale and domestic construction, where a single or two storey building has less need for the structural strength of steel. But CLT now opens up new opportunities in building types more typically associated with steel and concrete. “The engineering has now reached the point where CLT can span floor areas that are getting bigger and bigger,” says Gardiner. When integrated with hybrid-builds, combining CLT with steel joints or concrete, the sky’s the limit.
In Australia the developer Lendlease has been an early adopter, kick-starting a number of major CLT builds. Their Docklands library was the country’s first multi-storey building that deployed CLT. At four storeys tall, the library for the City of Melbourne incorporates study spaces, a 3D-printing lab, a games-design facility, alongside a recording studio.
“One of the things that a client likes to do, is pass on all the contractual risk, for supply, delivery, and installation onto the subcontractor. This means that a lot of clients won’t go with CLT because there’s a lack of builders familiar with constructing the material – even though any competent builder would be able to put a CLT building together,” says Gardiner. “Because Lendlease does have expertise with this material, they’re able to take on that risk.”
Like most things Australian, the introduction of CLT as a widely adopted material will have to play catch-up to its built cousins in the Northern Hemisphere. But according to Gardiner, that catch-up could be fast. “CLT is now just another structural material, which we can design to do anything. It’ll get market-share quickly, and I have no doubt that there will be tall Australian buildings incorporating CLT as time goes on.”
The library’s building process represented an exemplary sustainable approach to developer-led Australian architecture, with CLT panels “cut to the last millimetre”. Importantly, a CLT structure will continue to have net environmental benefits, as wood sequesters carbon-dioxide, thereby reducing a CLT-building’s carbon footprint by 75 percent. The library has gone on to receive a Six-Star Green Rating – the top-gong for sustainable Australian buildings.
Brisbane and Sydney followed, with a number of projects that are ticking many Australian architecture firsts. The former will be the country’s tallest timber tower (at ten storeys), while the latter will be Australia’s first engineered-timber office tower. All Lendlease projects.