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Against The Grain

Metropolis Magazine, April 2003

John Letts knew he’d uncovered an archaeological find in England’s historic thatched roofs. What he didn’t foresee was his controversial role in the battle between tradition and progress.

A thatched roof is made of the most global and, at the same time, the most local building material there is. Thatch is everywhere, and has been since prehistory, but it’s different everywhere too. The Irish used anything from rye straw to gorse; on the coast it was seaweed, and on farms potato stems. In inland Japan, most thatch is miscanthus, a wild grass that grows on mountainsides. In England the ideal home is a thatched cottage with “roses round the door” --and 25,000 historic thatched buildings cannot be altered without the consent of local conservation officers. “Thatching keeps the fabric and preserves a way of life, a culture, a heritage,” says Peter Evans, former head of craft training for the British government’s Countryside Agency.

No one denies that the British love their thatch, but for decades thatching traditions have been succumbing to a twentieth-century system of big agriculture, capitalism, and homogeneity. Ironically it was a Canadian scientist who inadvertently discovered a way to bring them back.

Archaeobotanist John Letts remembers the fall day in 1993 when he found himself analyzing what may be the oldest wheat in England. As a research associate in the Environmental Archaeological Unit of the Oxford University Museum of Natural History, he was analyzing seeds from the fire pits of a medieval village--” trying to build a story about medieval agriculture from bits and pieces of plants, bugs, and bones” -- when a colleague walked in with a shoe box, and turned Letts’s world upside down.

The man with the box said it held thatch dating from medieval times, probably the sixteenth century. Letts doubted it. “I said, ‘That’s impossible: wheat decays. It turns into compost,’” he recalls. “But this old thatch was so well preserved. And it contained strange wheat types, including a rare variety called rivet.” Letts knew that rivet wheat had all but disappeared by the mid-nineteenth century.

The incredible sample had come from James Moir, a building historian for English Heritage (EH), the government body responsible for preserving England’s historic structures. He had rescued it from a medieval building in Buckinghamshire that was being stripped of its cereal straw--the traditional material in most of England--and rethatched with water reed. Moir recognized the contents of the shoe box as part of a “base coat.” Thatchers usually recoat a straw roof every few decades by stripping off only the decayed part of the most recent layer and adding a new layer. Traditionally the base coat is not removed; it remains on the rafters from the time the house is built.

It took an archaeobotanist to see the sample as the miracle it was. In Letts’s eyes, it was an ancient storehouse, a five-century history of agriculture, chronologically arranged, complete with weeds and insects. “Once that shoe box arrived, my life changed,” Letts says. “It was clear that this was going to change our view of medieval farming. Ted Collins, a professor of agricultural history at Reading, practically had a heart attack when he saw it. ‘I’ve been lecturing about this for forty years,’ he said, ‘and now I’m holding a real sheaf of medieval wheat in my hands.” Within a few days Letts had written up a unique proposal: to excavate old thatched roofs as a type of archaeological dig.
Letts knew that thatch had never been studied as a record of farming. “No one had really looked at medieval crop plants very carefully before, “ he says. “Today, to identify a plant, you crush it up, extract the DNA, and run it through a machine that tells you what it is. You don’t look at the leaf. You don’t look at a flower.” Letts looked at the leaves and the flowers in that shoe box and saw in them clear scientific evidence of the relationship between man and his environment, back when the two were completely intertwined. But that ancient connection created an unwelcome overlap between two subjects that twentieth-century academics have typically disassociated. EH funded the department where Letts worked, but at first didn’t want to support his research. It “slips,” Letts was told, “between pure archaeology and building history.”

Letts began excavating and recording medieval thatched roofs anyway. “They [EH] gave me a token amount at the beginning that did allow me to examine two or three roofs,” he remembers. “But then I realized, ‘Oh my God, it’s all over the place!’” To find the old roofs, Letts sought out thatchers. “I needed to interpret the archaeological record I’d discovered on the roof,” he says, “and to do that, i had to … learn how thatch goes on. There was nothing written on that.” Thatchers were helpful, teaching Letts all they knew about the craft. “They talked about the finish,” he says. “They drove me around and showed me different roofs they’d done.”

Letts learned that in most of the country, if a building is old enough to be listed as historic, it was probably originally thatched with straw. But in recent years thatchers have been replacing cereal straw with water reed. Water reed is not attached to the undecayed part of a previous layer like straw but nailed directly to the rafters. To get a clear shot at the rafters, a thatcher has to strip off whatever thatch is there, and maybe retimber the rafters as well. “By definition,” Letts says, “every reed roof is a new roof.”

To thatchers and homeowners water reed is a high-performing material. But it presented a problem for Letts: the replacement method didn’t allow an archaeobotanical record to survive. Soon Letts was motivated by not just scientific curiosity, but a sense of crisis. “I realized that I had to go take rescue samples, and record them as quickly as I could, because the next month they might not be there. I had a duty to rescue them.