It was so decayed that the wind was blowing in windows. But after two years of meticulous work the Great Palm House is ready to reopen, writes Jane Powers
When it was built, in 1884, it cost just under £800 and took six months to erect. A hundred and twenty years later it has taken two years to restore and rebuild, at a cost of more than €14 million.
As it happens, the Great Palm House at the National Botanic Gardens, in Glasnevin, Dublin, could have been considered a bargain when it was built, for that year a single orchid fetched a record price of 1,000 guineas, or £1,050, at auction in London. And the palm house it replaced had cost £4,000, lasting just 25 years before it was declared unsafe, its timbers irreparably rotted and its engineering so poor that it swayed in high winds. Not to mention that its barn-like appearance was universally reviled. William Robinson, writing in the Gardeners' Chronicle, fulminated that it was "a hundred degrees too ugly" and that compared with the adjacent "Gibson's Venus" of Turner's curvilinear range of glasshouses it was "a hideous gutta-percha faced Amazon of Dahomey".
After this expensive white elephant of a disaster, the director of the gardens, Frederick Moore, was keen to have a speedy and economical replacement. The £800 palm house, which was made of wood and iron, was prefabricated in the Scottish town of Paisley by James Boyd & Son. It was shipped to Ireland in pieces, then assembled on site: a Victorian flat-pack greenhouse, 65 feet high, 80 feet wide and 100 feet long. That it lasted as long as it did was miraculous, as it too had serious faults.
Part of its problem stemmed from the combined use of wood and iron. This became horribly apparent in 1995, when a gale blew in a wall of windows. As the gust exited, a section of the roof opposite was blown out. Ciaran O'Connor, an architect at the Office of Public Works, was in the gardens at the time, working on Turner's range.
The damage to the palm house was so great that "we had to do a survey of the structure to see what the condition was". The results were scary. Places where the wood and the wrought-iron frame had met were eaten away. "The timber was completely gone," he remembers. "I knew it wasn't dry rot, or wet rot, but what was it?"
Chemical tests showed ferrous oxide from corroding metal had reacted with the tannic acid in the wood, which had then disintegrated. "A lot of the key points of connection, which were supposed to be structural points, were worthless." Also, the supporting iron columns had been unevenly cast, compromising their load-bearing potential. They were also losing carbon and becoming progressively weaker. "The building was so unstable that the metal frame was coming away from the back wall. I could put my hand through the gap," says O'Connor. "In storms you could see it flexing."
Panes of glass occasionally slipped out of place, because of corrosion and the movement of the building. When one pane was found plunged in to a palm, like the blade of a guillotine, the house was finally closed to the public.
When the question arose of what to do with the palm house, the gardens' recently retired director, Donal Synnott, urged that it be repaired rather than replaced. Vast and rounded, like a jelly mould, the Great Palm House is as much a motif of the gardens as is Turner's elegant series of glasshouses. Putting something else in its place would have irrevocably changed the character of this horticultural haven.
The restoration of the Victorian edifice was a vast project, but it was not the first such undertaking. In the 1990s the Turner house was restored, leading to the development of new techniques for working with 19th-century iron.
O'Connor and his colleague Gerard Harvey reused their methods on the palm house's antiquated iron. Having wood as well as metal required them to devise yet another solution to prevent the catastrophic chemical reaction that had eaten away the old framework.
Then there was the problem that the house had never been sturdy enough and so required strengthening. Cross braces were the obvious solution, but they would impinge on the beautiful airy volume and interfere with the plants. A brainstorming session with Pearse Sutton, of the O'Connor Sutton Cronin engineering firm, led to an ingenious solution. The raised walkways that encircle the structure would be reinforced, becoming, in effect, horizontal beams. Then they would be tied to the back wall, where a sheath of reinforced concrete would transfer the stresses and strains to the ground.
But before anything could be done the house had to be cleared. The tropical jungle that had enthralled visitors for more than 100 years had to be dismantled. All had to be moved: the towering palms, the cycad collection and the house's most asked-for inhabitant, the banana. Almost everything was moved to the gardens' other houses. "But the very, very tall palms had to be sacrificed," says Paul Maher, the gardens' curator.
Yet the trees' genetic material is safe, as the garden staff had collected seed. "We have hundreds of babies coming up," he says. The felled trees have supplied more than seed: portions of their trunks are being reused as bases for growing epiphytic orchids.
The restoration process was a project of heroic proportions - involving thousands of fiddly bits. The building was taken down piece by piece, then, after usable elements had been repaired, put back up again. The scaffolding was left in place while the parts were being overhauled at a workshop in Santry. The framework was used as a reference grid, ensuring the refurbished glasshouse was re-erected exactly as before.
Much of the original material was recycled. "Every piece of metal was tagged," says O'Connor. "That brass tag followed each piece all the way through all the work: in to the workshop and back. Nothing was lost." Not even the doorknobs. The quality of the restoration was recognised last night when it received an Irish Architecture Award from the Royal Institute of the Architects of Ireland.
The contractor, John Paul Construction, was extraordinarily conscientious about the plants near the site, according to Maher. "They even managed to save an important specimen of the shrub Distylium racemosum that was planted about six feet away from the building." The palm house's decayed timbers were not salvageable, but a Dutch firm in Burma supplied sustainably managed teak. The original paint tint was re-created by General Paints, in Co Kildare. Six coats of the gentle creamy white were applied.
A computerised climate-control system has replaced the clapped-out heating and ventilation systems; lighting has also been added. The two side wings of the house are being replanted so that orchids and unusual flowering plants will greet the Taoiseach, Bertie Ahern, on Monday, when he reopens the building.
But what of the planting for "the jungle house", as generations of north Dublin children have dubbed the vast bubble that is the main volume of the Great Palm House? "We want to give the palm house and its atmosphere back to the public," says Maher. "People like coming in from the cool outdoors in to a hot and steamy jungle." A planting plan should achieve this aim.
Planting will be delayed until November or December, says Maher. "It will give people a chance to go in and marvel at the architecture. Once growth starts it'll be fast, and the architecture will be obscured for another 200 years."
The National Botanic Gardens are open from 9 a.m. to 6 p.m., Monday to Saturday and 10 a.m. to 6 p.m. on Sundays. The renovated palm house open to the public from June 1st.
