The Flimwell Woodland Enterprise Centre demonstrated that the South East coppiced Sweet Chestnut could be a genuine timber material. With demand for Chestnut as a building material unparalleled, the ground-breaking Woodland Centre is well underway with phase 2, this time applying the treatment to Douglas fir for the centre’s eight cruck-frame work units.
It is a relatively well-kept secret that South East England is one of the most wooded regions of Britain. Tree cover amounts to 14% of the regions land, including Surrey, the most wooded county in the country. Extending from Kent at its most easterly edge across to Hampshire and Bucks west of London, it surrounds the capital and is, by common consent, the most economically dynamic part of the country. Much of the work of the construction and building industries is focused here after all. With the construction sector beginning to think seriously about sustainability issues and giving attention to ‘transport miles’ when sourcing materials, the opportunities for those working to promote local timber as a viable building material finally seem to be coming into play. Even so, in recent years, the use of locally-grown wood as building material has been, despite the high level of tree cover, in the main insignificant. Because the majority of the woods are either protected and/or in private hands, used as amenity for the public, or contain a mix of relatively poor quality timber and coppice so far they have been ignored by both the forestry and construction in favour of other materials or imported softwoods.
The opportunity to link the significant quantity of locally-sourced and renewable timber growing on the doorstep, and meeting the demands of the building industry in the region has been regularly noted, but actual initiatives to translate this into reality have been thin on the ground. One principal exception is the construction and work of the Woodland Enterprise Centre, (WEC) at Flimwell, East Sussex, situated in Yellowcoat Wood, close to the border with Kent, in the midst of thick High Weald forest. Over the course of the last ten years Woodland Enterprises Ltd, based at WEC, has championed the rebirth and re-introduction of local timber use in construction through developing new ways of using some of the most widely growing trees found across the region.
Well known in timberbuild circles for its first building for its first building at the Woodland Enterprise Centre, Feilden Clegg Bradley Studio’s (FCBa Studio’s), 450m2 modular gridshell made from finger-jointed chestnut coppice, houses a multi purpose double height auditorium, education rooms and offices, and was completed in 2003 and the marked the completion of the first phase of building at Yellowcoat Wood. WEC is now adding a second showcase example of contemporary timberbuild structures which have been built from the extensive woodland resources it sits within.
At first glance, what comes across, as you emerge from the entrance lane into Yellowcoat Wood, is the scale of what the Centre is trying to pull off. Immediately in front are the two new, sizeable and tall adjoining workshop/offices – the first results of the WEC’s Phase Two. Here – locally-sourced Douglas fir is used both as cladding and structural material. The surrounding ground is being prepared for the remaining six industrial units for which planning consent was granted in 2006.These will complete the second phase of the Centre project by mid-2008. A short distance away, is the original FeildenClegg chestnut gridshell building, surrounded by trees and foliage; and the new arrival underlines the scale of WEC’s aspirations. Nearby, the experimental Pyrahut structure, built and exhibited at the 2005 Weald WoodFair made to test and prototype the framing and cladding systems used for the new workshops languishes under oak trees a few yards to the side of the site. A Phase Three is also happening: Adventure Rope, an adventure structure manufacturer who uses round timber poles and rope is looking to relocate on the site and their initial workshop/office design is finished. ˜A ship in the forest’; waiting for the ink to dry on the contract for it to happen. And all around further forest.
Photo: David Saunders
Looking at the first pair of industrial units, what is immediately apparent is the sense of scale they evoke; the word massive comes to mind. Their height – (eight metres to the roof ridge) – is in part a function of the striking double-arched entrance gables, the weather protecting roofing leaning out, over the front entrances of the two units. The roofs are steep, 70 degrees, and evoke something atmospheric, pitched between a Gothic and almost pre-modern sensibility to the building. WEC’s intention is to show that locally-sourced timber structures can be used competitively for buildings usually made from steel or concrete. Those involved also want to repeat the gridshell’s success story, which in effect created a market for the locally plentiful chestnut coppice.
Cruck frames 1 & 2 before their fit outs and below, cruck frame 3 complete: Photos above George Sinclair and below Ioana Marinescu
The application of Sweet chestnut to the FCB gridshell design, was built on nearly five years of research and development into low-grade chestnut coppice as a building material. Directly inspired by the experimentation into small-diameter thinnings by John Makepeace’s Hooke Park in Dorset, the team who built the first WEC building “comprised of WEC’s project manager, David Saunders, FCB’s Andy Couling, InWood Development’s Nigel Braden and Neil Thomas from engineers Atelier one – worked on, tested and with facilities at BRE demonstrated that chestnut as a material was both structurally strong, naturally durable and responded well to new joining and gluing techniques. They envisaged that this research and demonstration work with chestnut could lead to developing a market for the material, and so help to restore the local rural economy. You can find this story of the WEC gridshell building and its application of chestnut as a structural and durable cladding material documented fully here. Without going over old ground completely the article points out how abundant chestnut is across the South East, there being around 20,000 hectares spread from Kent through to Hampshire, and how those involved at Flimwell’s WEC, within a parish with its long history of coppicing, foresaw their research and showcase building as ways to develop a new construction market for the low-grade, and small diameter material found in woods across the region. Several years later all that work has been vindicated: there is now a thriving chestnut cladding market serving the building sector at both regional and national levels. Lamination of sweet chestnut into glulam beams is also developing into a significant engineered material2 and the signs are, with sustainability on every specifier’s lips, that demand for locally sourced wood is on an upward curve. As Saunders says, “it’s exploded, and not just with the cladding. Demand is outstripping supply, there just aren’t enough chestnut coppice cutters out there at the moment to bring in the wood.”
WEC, however, was never only about growing a market for one particular regional tree. and both economic and site master-plan envisioned a thriving forest economy home to a variety of buildings facilitating various forest-related industries emerging within the Centre’s boundaries. WEC’s original prime movers, David Saunders and Inwood‘s Nigel Braden were joined by Green Oak Carpentry and Steve Johnson of Architecture Ensemble, (both at the time fresh from the Downland Gridshell across the other side of Sussex, where Johnson had worked as Edward Cullinan’s project architect) and began turning their attention to extending the phase 1 work. This year the Phase 2 timber workshops are underway, marking another milestone in both development and realisation of Woodland Enterprises vision; WEC as host to a whole cluster of small woodland industries, furniture companies, carpenters, sylviculturalists working with, and using materials from the woods which surround their workshops and offices. Phase 2 provides buildings for these forest industries. The eight industrial units stand a stones throw from both the forest and the first gridshell building. The first two industrial sheds should be handed over to their new owners before the end of the year, built this time, with another locally-prevalent tree, Douglas fir, in this instance sourced from the National Trust’s Leith Hill woodlands, some fifty miles away in Surrey. The workshop units are heavy adapted cruck-frame structures, rather than a repeat of light-weight shell structures, the aim being to show that industrial buildings could be built at price comparable to mainstream steel and concrete ‘sheds’. With the first units almost complete their presence conveys a much clearer sense of the long-term dream of what Saunders and Co running the Woodland Flimwell Centre are confident will become.
The original masterplan for Flimwell always envisaged workshops and these Douglas fir cruck-frame structures originate from some earlier SEEDA-funded work done by Architecture Ensemble’s Johnson for another site; Bettshanger Colliery in Kent, for which Johnson had developed a live-work space design. Steve Johnson’s original live-work scheme envisaged a cantilevered four-pin arch glulam post and beam system. But then the stand-alone industrial unit was downscaled and Johnson’s design began to be rethought. ˜It was pretty heavily economically driven” recalls Johnson, when the need for a cheaper system became apparent. Working with Green Oak Carpentry and Buro Happold’s timber engineering team, Green Oak’s Andrew Holloway suggested a cruck-frame design flexible enough to be prefabricated offsite. Johnson had already designed a large three-pin arch glulam workshed for Green Oak’s yard in Hampshire. Considerably larger, and using much thinner timbers the shed’s A frames turned into the Flimwell workshop units predecessor, with Holloway being able to demonstrate the economies needed. Much of the research was done during 2004, with funding support from a Leader+ rural grant, SEEDA and East Sussex County Council. A prototype, the Pyrahut, was developed, primarily to test the bolted framing and SIP type cladding system, this system being envisaged as the most effective for competing with the industrial steel shed mainstream. The experimental structure was built and completed by the end of the year.
Johnson, a timber architecture specialist, sees the cruck-frame as ˜a very elegant system”; providing an all-in-one wall and roof truss which acts in compression, and is particularly strong against heavy wind loads, including the maximum strengths found in Britain – according, he says, to the results of Buro Happold’s engineering tests. Although such frames have become quite popular as a high-end domestic timber structure approach, Johnson believes these are the only industrial cruck-frames to have gone up since Alec French Partnerships, Sheepdrove Biodiversity Centre. Over near Rochester, Kent, the Shorne Wood Visitor Centre by Lee Evans Architects also employs a laminated chestnut cruck-frame; and the sense is that these contemporary interpretations of a very old, even archaic, building technique are only a first chapter.
On my visit the system evoked a real sense of presence. Structurally, the workshop units apply, or at least update the cruck frame principle of removing the need for horizontal beams. Traditional crucks were just that, following the natural curved timbers until joined at the apex. Here the adapted version use a series of sawn timbers bolted together to form triangular trusses; first a vertical post, joined by a two-sectioned linking beam onto the third roof angled beam, rising up to the roof’s ridgeline, where it meets and is joined to its opposite from the other side of the unit. Comprising four trusses per wall face, the whole double unit structure consists of twelve trusses divided by six metre bay gaps along the walls. Transparent polycarbonate roofing runs along the arch ridges, providing natural lighting into the upper floor. Where the partitioning walls meet between the two units, the frame trusses push up to make a striking v form.
The workshops units are also clad in Douglas fir. On all of the elevations, including the roof slopes, prefabricated horizontally clad rainscreen panels have been attached. These were constructed off-site at the Inwood yard, just ten miles down the road, and have been fitted by the buildings carpenters, father and son team Wayne and Chris Pritchard. Inside the paneling system are other sustainable features; which include sheep wool insulation in the cavity, and Fermacell linings on the inside walls. Cork has been used to support the valley gutter system while the window joinery uses the new Accoya engineered wood, again manufactured nearby by Westgate Joinery.
The total cost to shell specification is about £125,000 per unit, with a size of 90 sq metres per unit. Anyone who buys a unit finishes off the fitting out, bearing the costs but also the design freedom. The result doesn’t match pound for pound with prefabricated mainstream industrial systems but with steel prices continuing to rise, Johnson, and to a certain extent, Saunders, feel confident that they can demonstrate the units as credible and highly sustainable alternatives to what is generally on offer. At present live-work spaces are outside WEC’s overall plan, although Saunders is adamant that all those who eventually buy the remaining units will have some direct relation to woodland industries.
The lessons learned from the construction of the first two workshops has led to some discussion about refining the design in order to reduce costs to those originally envisioned. The option to replace the numerous steel bolts and joining plates with timber pegs and joints is being considered. Indeed Buro Happold’s project engineer, Jonathan Shanks spent much of his Bath university PhD testing the performance of timber jointing4; and from a traditional carpentry perspective there must be quite an attraction for these next iterations to push towards such a fully crafted approach. All-wood crucks would possibly reduce the embodied energy used in manufacturing the steel. However further significant design development would be needed achieve an all-wood structure with the as yet uncertain economic benefits over the metal bolted system. While possibly a purer and more elegant system, my sense was that whether or not this happens depends on who is or isn’t willing to underwrite the additional research hours.
Further down the path, there is the Adventure Rope Company. factory, which Johnson is calling a round pole design. Rounded Softwood poles will reach vertically up into the sky, extending out of the factory’s roof.
Photo: David Saunders
But will it all happen? If Saunders and the Woodland Enterprise team get the industrial units occupied as they were originally envisioned; by small wood-using companies taking advantage of the surrounding timber resources – Flimwell will have met its ambition of developing a fully functioning local forest industry, a significant accomplishment and contribution to the potential revitalization of rural economies. This is not too far from the original master-plan – which featured a visitor centre, workshops, offices, and energy technology demonstration, retail and a village and community hall; a shared use building. Even if only part of this is accomplished, the claim that Flimwell is continuing the work begun at Hooke Park, is in effect picking up the baton from Hooke will be true enough. Certainly for Saunders, John Makepeace’s vision for Hooke “made a huge impact on me. With both his forestry background and his knowledge of local wood issues, Makepeace was to Saunders somebody with real understanding; and the notion of using wood from the adjoining forest “for growing your own building was hugely influential” He adds, “Makepeace, using ‘small diameter low-grade’ wood “completely reversed the thinking. For the first time one didn’t have to fell a two hundred year old oak, but could use 30 year old thinnings and leave the oak to mature. Along with the spirit of Hooke hovering over the project, Saunders identifies the emergence during the nineties of a reinvigorated green oak framing movement, and this, along with certain examples of developing local timber supply chains, has increased the volume of regionally-sourced wood used in the construction industry. He recalls the mid-eighties, – Hooke Park’s heyday – when Flimwell first seeded itself as an idea which could work in the local context. It took ten years to really get to seriously beginning recalls Saunders. ˜In between we had the 1987 windblow, which distracted us for a while.”
It has taken time, but the Woodland Enterprise Centre at Flimwell has taken up the challenge Hooke Park left hanging in the air when it closed down. Saunders often talks of Flimwell as Hooke plus added pragmatism. No grand rural iconic gestures of Hooke’s Frei Otto variety. He feels the experience with chestnut has proved that timber in the South East can reach the quality required for volume building, and is strong and durable enough for use across a diverse spread of building types, both old and new. The further aim of the new industrial units is towards developing markets for alternative species such as Douglas fir and Larch “with their relatively short rotation of sixty/seventy years. In-wood’s Nigel Braden echoes this, believing that home-grown Douglas fir competes well with second-growth Canadian imports. Structurally strong, produced at C24/C28 grades, Braden expresses surprise that more forestry people aren’t growing the tree.
With the new work units, Flimwell has in effect doubled in buildings. Soon with other workshop buildings and Phase Three on site, WEC should be able to provide a working, pragmatic showcase for locally-sourced timber. And then there’s the architecture. Saunders ponders the range of building types, each demonstrating different materials and designs. Along with a number of other buildings across the South East, what is now emerging at Flimwell are contrasting expressions of a regional vernacular for the early 21st century. With local materials gaining profile and a wider acceptability, the odds for such a contemporary South East building culture growing deeper roots are looking good.
A version of this piece first appeared in Green Building, Volume 17 no 3, Winter 2007