Astley Castle in Warwickshire by Witherford Watson Mann Architects is the winner of the Stirling Prize 2013.

Beating shortlisted projects Bishop Edward King Chapel in Oxfordshire, the University of Limerick Medical Centre, the Newhall Be development in Harlow, Essex, the Giant's Causeway Visitor Centre in Northern Ireland and the Park Hill renovated estate in Sheffield, the modernised castle becomes the 18th winner of the prize that has been previously won by Richard Rogers Partnership, Zaha Hadid Architects and last year’s winner Stanton Williams for the Sainsbury Laboratory.

Astley Castle is the first project dealing with a historic ruin or existing building to win the prize, yet due the award's officiator RIBA being unable to secure a sponsor, the prize was without its usual £20,000 monetary award.

In the following conversation, Disegno talks to principal architect William Mann about the project’s evolution and what winning the Stirling Prize for the best European building designed in the last year means to Witherford Watson Mann Architects.

The project began as a competition for the Landmark Trust, what do you think contributed to you winning the commission?
There were 12 firms invited to put ideas forward in a short design competition. The scheme we proposed at the competition stage is broadly the one we’ve built in terms of the overall idea of stabilising the ruin with the new structure. Also the idea of partially roofing over the 15th or 17th century rooms as external courts creates a feeling of a certain completeness, harmony and of being rooms rather than just holes. The Landmark Trust appreciated that rather than having a new project that had its own foundations and roof, or having to do works to invisibly reinforce and save the ruin, they had not quite two for the price of one, but a scheme that did both at the same time.

History isn’t something that happened to other people, or that’s finished. This is a castle that has grown over eight centuries - it was added to in the 15th century, 16th century, 17th century and 19th century and there was this big catastrophe with the fire in 1978. In a way we treat what we add in the 21st century in the same way - it’s just another layer on top of all the additions already there. We were latecomers; we were sixth in line and we added to that overall mix.

How difficult was it to design within a shell that had been destroyed by a fire and to restore a structure that had been added and modified several times prior to that?
In terms of difficulty, there were eight centuries of construction. Obviously people built differently in the 12th century from the 15th, to the 17th century. We had half a dozen different construction techniques and two or three different states of decay. By maintaining quite a limited palette of materials, quite a limited set of approaches and a strictly defined set of interventions at the same time, we responded to each junction with a detail that was slightly different to the rest.

However, there is a great sense of coherence to what we’ve done. My analogy is that for good musicians, the discipline or command of your craft is actually what allows you to improvise. There were a few simple rules we arrived at after a couple of years of working on it, which was we would only build new masonry on the lines of old masonry; any other partitions not on those lines, we would do in carpentry. The idea was that we would keep the ruin, we would build as little new masonry as possible, so we kept these big gashes from the ruin. All the rest was down to the sense of proportion, craft and discipline as well as responding to several different conditions in a way that had coherence.

The lighting uses the ruined remains of the fortified manor to create unusually shaped apertures to light the space - how did this become part of the overall design strategy? 
Castles are gloomy. Our approach was to show the ruin as an event. It wasn’t just something that you turned your back on and ignored and certainly not something that we would just reinstate. The idea was that it was a modern house within an ancient shell and therefore it has the qualities of a modern house, which are light and views.

The project demonstrates a very different approach to renovating a historic building by adding a contemporary layer onto the older ruin. Is this approach specific to this project or a statement on how all historic buildings should be treated?
Probably the answer lies somewhere in a grey area between these extremes. There is an idea of trades - the trade of masonry, carpentry or joinery - the techniques have changed a bit. In some cases you can do things that are bigger and stronger than elements that were available previously. In other cases, part of the reason we are using laminated timber is because you can’t get sawn timber in the sizes that you could during the Middle Ages. There are standard timber sizes now, whereas in the 15th century or the 12th century you probably just wandered into the forest, found a tree and made your roof out of that. I suppose there is an element of continuity of materials and an element of change of the techniques.

We were part of the team that did the final Olympic legacy masterplan and one of the things we were looking at there was how that area had grown up over time. I’d say that’s somewhere where we were doing exactly the same forensic sifting of the different elements of the landscape but at the same time, the same creative interpretation as to how all those different bits of different systems and different values could add up to be a special place now.

What does it mean to your practice to win the Stirling Prize for this project, especially as the first project of its kind as a historical insertion?
It’s relatively early in our practice’s career; we’ve been going for 11 years. To actually get this kind of recognition is a fantastic endorsement and vote of confidence. There is something special about being the first transformation of an existing building to win the prize. That’s how I like to talk about the project because it isn’t a restoration or repair or conservation, it is a transformation in the sense that it’s made it into something that it never was before. Castles are strong and dignified, this thing that’s a mixture of ruin and house is soft, porous and opens up to the elements.

So much of how we talk about architecture and communicate architecture is through photographs, but this is something that has been visited by two or three juries – a regional jury, the shortlisting jury and then the final jury. They came for several hours and looked at it in great detail. While there are some awards that are judged on paper where it comes down to the quality of the visual presentation, what makes this an award that has a lot of value is because the judges go there and look at each project so carefully. This is an award where the experience of the architecture is really important. While it’s a building which is photogenic from some angles, there are bits that are very hard for photography to capture. This has stood up to hours and hours of careful scrutiny which does give a statement of confidence and an affirmation that we really value.

INTERVIEW Manijeh Verghese

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