With all the buzz of last month’s London Design Festival sadly dissipated, what legacy do landmark projects like dRMM’s spectacular Endless Stair leave behind? Architect Alex de Rijke tells us how the towering sculpture came together, and more crucially, how it comes apart.
What’s the structural logic behind Endless Stair?
Alex de Rijke: The basic unit is an L shape of cross-laminated timber, one strong joint. It’s a structure that we’ve used in various ways throughout the whole thing. So there’s no primary and secondary structure, that’s it. In some places the flights are propped – it just became impossible to achieve without some support – but apart from that it just works with its own internal structural ability. It’s appearance is also an expression of the fact that it can be changed, that was quite important. We were interested in what happens to it afterwards and we designed it specifically with recycling in mind. Part of the reason it looks how it does is that you can unbolt it and change it.
How will it be re-used?
As staircases, I think. We’re open to offers about a use. A specific public use. Maybe in an educational context or in a gallery – it’s up to the kind of proposals we get really. It can be split, so it could be 15 different stairs or it could be reconfigured as one, two or three. Maybe we should have a competition to solicit the best proposals.
Endless Stair is a collaboration with the American Hardwood Export Council (AHEC). Did they ask you to use tulipwood as a material?
Well AHEC said we’ve got all these different woods, and asked what we were interested in. I remember saying well I’m interested in what you’ve got too much of, what’s surplus to requirements. And tulipwood was suggested because there’s such an oversupply and it isn’t a high-grade timber. I was interested in that too. The thing I really liked about the samples was the variety. Not just the tree in itself but the regional variety because of the different climates.
And that manifests itself as these streaks of colour.
Yes. So I remember saying we’ll have the cheapest and the widest variety and we’ll mix it all up and make something special from it. AHEC was always keen on doing a cross-laminated timber experiment, I guess that was the reason for choosing dRMM, because we know all about it. We’ve done it longer than anyone in the UK and it seemed like a natural experiment for us to do. And I think the ongoing analysis of it will be really important to the project. You know it’s tempting to see these things as ‘here today gone tomorrow’ – all the ephemera of a festival – but the most important thing is the whole life cycle monitoring of it. In terms of energy and carbon, it will be a useful bit of research.
Projects like this can end up as follies, but yours is a real piece of research as well.
Well that’s definitely why we were so attracted to it. Because AHEC was quite clear about its agenda to document this as a research project. And Ben Evans, the director of London Design Festival, was quite clear about making a structure that wasn’t just an object. I like that because I’d written a kind of critique of festival structures, well classified them into different types, and came to the conclusion that we wanted to do ‘useful art.’
Not something you just stand and look at.
Yeah. And Ben wanted it to provide views that you wouldn’t normally get. As well as viewing it. And we very quickly thought of a stair, because stairs are pretty special places, in architecture anyway. They have a bit of everything, composition and structure, proportion and legality issues around safety, so we thought actually it was quite a rich area to deal with, making a stair. We’ve actually had to design quite a lot.
And engineer quite a lot.
Arup worked on the engineering and when they did the de-propping, they were amazed by how strong the structure it was and how little it moved. How far you can actually push this material.
Why was the structure fabricated in Switzerland?
Well first the lamination was done by Imola Legno in Italy. They generally make timber for the furniture industry and were happy to produce cross-laminated timber (CLT) panels from the timber supplied through AHEC in the States. A generic CLT manufacturer would have to stop the entire run in order to change wood for this one-off project. Whereas Imola Legno was quite happy to slot it in to its more bespoke production line. They then passed the panels to Nussli who are specialists in installing temporary structures. They have a factory with the expertise to do all the CNC cutting, so we could give our drawings straight to them to program the computer that cut the timber. And then we went there to test the prototype for weight, stress and to check the quality of the joints and it was really high. They’re the kind of specialist outfit that doesn’t really exist here.
And how did it arrive in the UK?
Well the flights were designed to nest. This saves space in transport. The 15 preassembled, stacked flights arrived, and were then craned into position and the balustrades and props put in.
It’s a neat idea to have a repetitive stacking logic to it. So you could plan things like the final assembly, almost from the start.
Oh yes, well we made lots of models to explore all these ideas. Physical models using the samples of wood we were given. We had the actual wood so we could work with its characteristics.