There is something about The Smile, the installation in tulipwood CLT (cross laminated timber) that has been designed and made for this year’s London Design Festival, that is light and joyous. Despite its considerable size, the quantity of material used, and the very careful planning and engineering that went into its design and construction, it is cheerful and makes you want to, yes, smile.

Much of this is thanks to its architect Alison Brooks who, given a brief by  client AHEC (the American Hardwood Export Council) to produce something that exploited the properties of tulipwood CLT, came up with the concept of a beam that curves up at both ends. Her happiness in the project, despite a lot of hard work and setbacks, is evident. She takes joy in it and that joy translates through into the object (no, building) that she has conceived.

This is not because Brooks is not a serious architect. She has excellent credentials as a designer of both housing and larger projects, particularly in education, and was part of the team that designed the Stirling Prize winning Accordia project in Cambridge. But she relished the liberation of the very different programme of designing the smile.

‘It’s fantastic not to be constrained by all the demands of a typical building,’ she said. ‘It’s liberating. It’s fantastic to focus on the experiential , the parts of creating an object. It helps you to understand space in a new way. Hopefully, it will open everyone’s eyes to a new environment.’

Another part of her joy came from her love of working with wood. David Venables, European director of AHEC, said, ‘With Alison, our relationship has been over 10 years. We first met doing lectures for architects in Germany, where she was talking about her pioneering use of timber for affordable housing. There’s a clever simplicity to her architecture, and a good bit of humility. Very quietly, she influences and changes thinking.’

Brooks, who is Canadian, has a particular love for cherry, a timber with which she has grown up, and is using it extensively on her new building at Exeter College in Oxford. In one area she also investigated using tulipwood glulam, only stymied in the end because her contractor, in the absence of British Standard data, was not prepared to work with an unknown material. It is a timber that is relatively new to Brooks, but one that she has taken to her heart.

‘I think it’s a very interesting wood,’ she said. It’s not heavy which is helpful;  it has character and it has a tight grain. I’m not a big fan of wood that has a deep grain like oak. I like not having little holes that can be filled and turn black. Sometimes you get an interesting sheen from woods like tulipwood and cherry, because they are relatively slow growing.’ There is also considerable colour variation in tulipwood, which Brooks enjoys. 

She was evidently in an excellent position to carry out this project, but how did she set about it? ‘Part of the brief,’ she said, ‘was that AHEC wanted tulipwood CLT to be tested and demonstrated as a series of construction products. They wanted what I designed to demonstrate the capacity and ability to do fantastic things structurally.

‘So rather than a decorative element or a small piece I immediately thought this has to be a structure that works with large components and the plated material. How could it use that material to show off and celebrate the structural properties of CLT?’

There was, she said, ‘an immediate appeal to making a cantilever. And the idea of using large format elements as plates and expressing their capacity means you have to turn it into a beam. These are four-sided elements that work very well in tension and compression. Wouldn’t it be fantastic to make a huge tube out of timber that cantilevers? It shouldn’t require a lot of additional structure to make the piece. And it could be stand alone.

‘It had to be an autonomous self- supporting structure. I thought of the diagram of beams in bending which forms a curve. The idea of being in that was interesting.’ 

And so The Smile was born. The CLT tube is an inherently strong shape, in the same way that a steel tube is. The curve means that it cantilevers from, effectively, a single point in the centre. There is an opening at either end offering views out. Visitors walk up the slope of the curve to enjoy this view, encountering a glass balustrade with a handrail to it that Brooks describes as ‘rather like the rail of a ship’. It offers, Brooks says, ‘quite an unfamiliar spatial experience. It has a playful quality – between a landscape structure and a building. And it creates spaces underneath.’

At one stage in the design, the sides of the tube were also curved, narrowing to a ‘waist’ at the centre, but although this added to the spatial excitement, it proved one curve too far for the manufacturing process. Even less feasible in structural and visitor safety terms was Brooks’ initial conceit, that she would have liked The Smile not to be fixed, but to stand freely on its base so that it could rock as people entered it!

She has however thought very carefully about enhancing the visitor experience. The tulipwood will be exposed both on the outside and the inside of the structure, something that is only possible with this kind of temporary building, which has no need for insulation. Although she has worked with glulam, Brooks has never had the opportunity to work with CLT before – she has tried to specify it but because for example of acoustic constraints it has never been possible to use it without a great number of additional layers. Here she is celebrating the material, precisely because it looks so different to softwood. ‘The main difference is that there are no knots,’ she said. ‘Glulam with softwood gives a knotty pine look, which is very rustic and not what I like. Hardwood CLT is knot-free.’

Small holes, drilled at an oblique angle through the wood, allow light to filter in. These are set in the least highly loaded parts of the structure and are an indication of where the stresses are. Brooks said, ‘Every time there is a change to the calculations, the positions of the holes changes.’

Brooks has evidently thought carefully about the way that The Smile interacts with light. During the daytime this will be predominantly daylight, but after dark there will be a strong but simple effect on which she has worked with the lighting designer. A beam of light will come out of each end, running along the ground and effectively elongating the structure.
Brooks may have been liberated from many of the constraints of detailing a building, but where such detailing is needed it is both simple and well-considered. So, there is a ramp to allow disabled access, leading up to the centrally placed door. The top of the structure is a simple membrane roof (a planted roof would have been nice but was not within budget).  Water runs down to a channel in the centre, which connects to a spout that throws it off the back of the structure. 

Brooks is so happy about the project that it is no surprise that she came up with the name of ‘The Smile’. ‘It was the first name we thought of,’ she said.