In the UK, 'design and build' generally refers to a form of procurement where the building contractor takes responsibility for the design of the building as well, leaving a limited role for the architect. In the USA, the phrase normally refers to the reverse - an architectural practice that also builds its own projects, generally private homes or small residential/commercial developments. A 'design-build' approach is also practised in several architectural schools, most notably the Rural Studio in Alabama where I spent a year, but also in Kansas, Parsons School of Design, the University of Texas and Washington State.

Here in the UK, there have been very few examples of practices taking this approach - Turner Castle for example. But it has hit the headlines again with the news that Tom Heatherwick, star designer of bridges and public art installations, is going to act as main contractor on the 300m2 Aberystwyth Arts Centre in order to 'liberate their working methods'.

It seems that the tipping point was the cladding, which "just wasn't possible for a contractor to price". We are used to architects developing bespoke material solutions for their projects - I think of the extraordinary lace concrete cladding that Caruso St John are using in Nottingham - but usually this takes place within a more standard form of contract, and often causes big issues in terms of nominated subcontractors, performance specifications and cost certainty. But for Heatherwick to take contracting into their own hands - particularly for a public building such as the Aberystwyth Arts Centre - potentially lays the practice open to far more risk and liability and also may expose the client to huge cost issues if things do not go to plan, as there will have been no competitive tendering process. I wonder how this sits with the procurement policies of the commissioning body.

But we also have sympathy for this approach. As architects we are fascinated by the potential to use materials in new ways and to test out fabrication processes in advance rather than designing purely on paper. Here at HAT HQ we have a workshop below our studio in which we hope to be able to do some of this, and Alex de Rijke says that they are planning to build a fabrication workshop near their studio to develop their work on engineered timber. Surely a process of prototyping means less risk in the end product than the traditional method of leaving it to the contractor to figure out, or the failures that every Cambridge graduate of my generation will be familiar under the heading of 'Corten Catastrophes' - where a good idea on paper ends up dripping horrible stains all over the place in practice.

Equally, with more architects trying to do small developments of their own - the awkward pocket sites that no commercial developer likes to deal with, a few units here and there - there is more incentive to turn contractor as well and take the whole package into one's own hands. At HAT we are also interested in this approach, Tom having worked in the past on similar projects with MOOarc. But for a public arts building? That's a brave step.