In many of the Cornish gardens there are stands of the great leafed gunnera. So it is at Carwinion where we stood, five of us, under one leaf sheltering from the rain, pondering the vicious spikes that cover the undersides and the stems. Later that day we were covering the zip-up bamboo house roof with them to demonstrate emergency housing for disaster areas to the European Bamboo Society gathering.

A couple of months later I was given a brief by the Eden Project to design and build a shelter in the landscape at Bodelva Pit; leaves came back to me – a large leaf for a plant-based project! Various leaf structures underwent the drawing process, with solutions in materials varying from steel and ropes to bamboo and canvas.

It was after seeing the initial research that Eden settled on a Camellia senses leaf to be sited in the tea-growing area of the project. Nick de St Croix had been helping me to erect the zip-up bamboo house at Carwinion and we got together to build a leaf that would be in proportion with Eden’s biomes.

On close inspection the camellia, save for small serrations from midway to the tip of the leaf, offers only veins that return on themselves before minor tributaries filter out to the edge. It was the returning veins that gave us structural clues. A model of the main vein with returning veins was made and Eden was delighted. From the model, scale drawings were made – at 39ft the leaf would make the whole bush about 600ft high.

Big challenge

The humid tropic biome is enormous. We knew we were shooting high and a single laminated leaf proved to be an ample challenge.

A sweeping rollercoaster type jig was made out of scaffold tube and the main spine was glulaminated out of ash planking clamped down three layers at a time; 18mm birch ply protrusions were built in at the vein springing points.

This process started last January and a plastic tent was constructed over the entire length to heat cure the resorcinol resin used.

Although the interstices of the former were regular, because of the length and the need for clamping the ash finger-joints and the laminates simultaneously, clamps and taut liner straps were used.

Once the body of the spine was complete it stretched from Nick’s potting shed through his workshop out into the garages, leaving squeeze gaps at the doorways. It was time to move.

A unit at Ebley near Stroud was found and the first flat-bed journey for the main spine took place: it was lifted into the new spacious workshop and three months of intensive work started.

Nick, a genius at structural solutions, had come up with a system that consisted of the ribs springing from the plywood inserts in the main spine and cantileverings in a twisting curve and joining onto the mid-point of the previous rib; the ribs first increasing and then decreasing along the length to form the internal leaf structure.

Once the tapering, backward reaching boxing had been built on the plywood inserts we set about forming the large curved box ribs. Using 40mm ash wands, we split them in four along the length, leaving the box connections solid. These wands were bent into shape, cut to length, removed, glued up, replaced and clamped to bleed the glue, covered and heated to cure. This process with four wands to each of the ribs was slow but effective.

Birch ply cladding

After each rib frame was made, nodes were built into them to receive the joining point of the next rib. Each laminated rib was designed to be removable so that they could be planed and sanded, giving a flat surface to receive the birch ply cladding. Once clad, the underside of each rib was routered out to receive an ash bead so that the seen edge was not a ply butt joint.

With all the ribs constructed and sprung off each other, a series of curved ash laminated prongs were inserted into the outer edge of the shape formed by the ribs. These ‘ice hockey stick’ shaped prongs were housed in built-in slots to form the structure of the serrated leaf edge. By routering out a keyhole slot in the edge of a wide bead that ran down the whole length of the spine, we could then attach the canvas cover centrally and stretch it out to the sprung prongs. A rope was sewn into the canvas edge, fed into the keyhole slot and pulled along the length of the spine ‘sail style’. The next canvas length was marked, cut and sewn so as to shape the canvas over what is a highly complex vein system.

Once the edge was determined, more cuts were made, reinforced and clipped into place to make pockets for eyeletted inserts. D-rings were screwed to the rib edges and the forest green canvas leaf surface was laced over the whole frame with two lengths of red climbing cord and cleated onto the spine at each end. All the timber, both ash and birch, is untreated but waxed with an OS exterior finish.

The leaf is designed as an outdoor shelter so the stalk end rests on the ground and the tip is 2.5m off the ground, tilted slightly to one side so that at first sight from the pit edge and the visitors’ centre it appears to hover above the ground. In fact, it is supported at the stalk and two-thirds along by 100mm box section galvanized steel, dropped into corresponding sleeves in concrete footings.

Helicopter delivery

After an estimated 1,500 hours work, copious pairs of rubber gloves and dust beyond imagining, the leaf was ready. We had played with the idea of delivery by Chinook, but settled on road haulage. The whole thing was dismantled, loaded and strapped down for erection on site.

The Eden Project’s brief had been for ‘an elegant temporary shelter in the landscape’ from which to contemplate the extraordinary transformation they had made from a work scar to sloped terraced gardens. The project spells out a message of dependence and a warning about man and his ancient and contemporary relationship with the plant world at every stop along its path.

In making the shelter in the form of one leaf that defies structural likelihood, we trust that those who see it from afar, or sit underneath it, will be reminded of our total dependence on the plant world for our survival.