Softwood may have been the material of choice for timber architecture up to now, but hardwood has just made a dramatic entrance. 'It is simply the most challenging thing that has ever been built in cross-laminated timber [CLT]… anywhere,' says Andrew Lawrence, an associate director at Arup, about the gravity-defying 34m-long cantilevering curved tube devised by the American Hardwood Export Council (AHEC), London-based architects Alison Brooks and Arup for this year’s London Design Festival.
The Smile, as the project is known, eschews the usual European spruce for a fast-growing tulipwood from North American forests, that has been transformed into 12 huge cross-laminated panels ('the largest hardwood CLT panels ever made', says Lawrence) and is held together by 6,000 long steel screws.
'Almost every architect we talk to says we love CLT but we don’t like the look of it!' says David Venables, European director of AHEC. The organisation has been experimenting with hardwood structures for some years now and believes the material offers the same weight and density as softwood but twice the strength and a far more appealing aesthetic (fewer knots and a classic tight timber grain).
Hardwood may cost more, acknowledges Venables, but you also need to use less of it. 'In the future we will see panels where three of the layers are softwood but the outer layers are tulipwood, for instance,' he says. 'And we will see it used in higher-end buildings where appearance really matters,' adds Lawrence. 'What’s so fun about designing in wood,' he adds, 'is that architects and engineers have to work really closely together and the way a structure is made and engineered becomes part of the architecture.'
Even more exciting is the fact that CLT is carbon neutral, sustainable (the 240 cubic metres of tulipwood used to create this particular ‘flying pavilion’ were replaced in less than five minutes) and, in the words of Alison Brooks, 'connects us back to nature in a way that is not nostalgic or rustic. It’s a material of the future.'