Roofs that strut their stuff

James Potter of Waind Gohil + Potter Architects looks at the potential to take a fresh look at roof design and create more sophisticated structures.

On the island shores of Papa Westray lies the Knap of Howar. Having visited this remote corner of the Orkneys I feel qualified, sort of, to confirm this archaeological site as slightly underwhelming were it not for one fact: the Knap of Howar is approximately 5,000 years old and the best preserved house in Northern Europe.

Mindful of this, it’s hard not to be impressed at how intact it remains. But the one pesky stumbling block limiting the Knap of Howar’s ability to get an up to date EPC is the absence of a roof. Like everything on these windswept islands, if it stands above two metres tall it’s an open goal for mother nature to blow it flat or away altogether, so it’s unsurprising that all but the
semi-sunken stone walls is long gone. Yet to understand the design of these remarkable buildings is to understand the missing roof.

This would have been the most daring and sophisticated element of the construction. Timbers or whale bones forming a tent like structure, lashed together and faced in hide and turf. One can’t help but wonder whether plastic membranes and sedum are that far removed from these ancient origins given how much time has elapsed.

Roofs as a building element are no more important than walls, but the primary weathering element of any shelter is the roof and the fundamental of any building is to give shelter. On that reasoning they are special, and, as a young(ish) firm, roofs are something we have attempted to look at with fresh eyes.

At our New Oak house design the roof structure was a mixture of stressed plywood skin and oak struts to stiffen, the former allowing us the opportunity to free up the positioning of the latter. None of it was feasible without an engineer (Webb Yates), architect and contractor working closely with the final pattern of supports agreed on site, not on the computer.

Of course, there were other equally valid ways to form this roof, however that in no way renders the decision to implement the chosen structural system as defunct. There is simply a wider choice of materials and structural techniques available now to form a roof from and in turn create something individual. Roofs, by their nature, produce ceilings. These often plain surfaces can be expansive and undervalued, but their simplicity belies

their importance. Earlier this year we completed our competition winning ‘Skyhut’, a simple wooden cabin for glamping in the Welsh wilderness. Wales has some of the darkest skies in Europe, making it ideal for star gazing: at the touch of a button an actuator raises the unassuming roof leaves and the ceiling pivots to the vertical revealing views of the stars from the comfort of a bed – if it’s not raining.

What’s interesting about the Skyhut isn’t the technical feat of building an opening roof but the perception of the same little space, with and without a roof. When closed the cabin is well insulated and comfortable in all seasons, but with the roof open it’s as if the ‘building’ has gone and one is left in a field next to some sheets of plywood.

We are a long way from reaching the dizzying heights and refinement of, say the fan vaulting of Westminster abbey, but in our own way we seek new yet functional ways to express the raison d’etre of a roof. Perhaps a little more consciously than those of old…or perhaps not?

For example, how did the oak framed roof of the ancient barley barn at Cressing Temple remain so fine? Unlike the Neolithic Knap of Howar the barley barn remains very much complete and the oldest timber barn in the world. But I remain sceptical as to whether the craftsmen who made it just happened upon such a handsome structure: someone had their eye on the prize in medieval Essex.

Indeed, whether the contractors building the Knap of Howar were looking to find joy in the expression of a truss is anyone’s guess but they still made the roof the most exciting part of the house, or rather the roof demanded or facilitated the most
interesting construction, who knows?

James Potter is a director of Waind Gohil & Potter