Shorne Wood’s Sweet chestnut cruck frame
Not only has the Flimwell gridshell project kick started interest in Sweet chestnut as cladding and joinery material, it has also seeded an awareness of the material across regional planning, governmental and related architectural communities. Immediately after the turn of the millennium Mark Read, project manager at the Shorne Wood Country Park, just west of Rochester, Kent had been following Flimwell’s progress only too aware that his 288 acre woodland contained nearly 100 acres of coppiced chestnut; potentially a perfect site to pick up on the use of local materials for the new visitor centre planned for the woodland park. From that time, late 2003, Read was part of a team which developed a brief that foregrounded the use of local wood resulting eventually in a landmark chestnut cruck-frame building in early summer 2006. Although again, as with WEC phase 2, somewhat long in its journey from conception to completion, the building’s brief has also since filtered through into Kent County Council’s policy commitment to using local sourced materials’ wherever possible across its procurement programme, including sweet chestnut.
Another showcase for the growing number of examples of buildings applying locally sourced materials to a timberbuild design that stand out today is Shorne Wood’s Visitor Centre. The centre evokes an organic aesthetic, with a beautiful curved roofline clad in cedar shingles, a spacious interior acting as restaurant and interpretation centre, as well as a first floor environmental education/conference space and mezzanine with office and admin rooms.
The ground floor interpretation area makes full use of the building as a teaching and learning instrument to convey the sustainability issues inherent in local materials while also demonstrating their use in contemporary building. Designed by Canterbury practice Lee Evans Architects, the centre’s brief was for a ˜robust, unique and sustainable” building, which could act as an environmental exemplar for Shorne Wood and the region. Steve Johnson of the Architecture Ensemble based his earlier design of the building around a fusion of organic with more rectilinear design features; envisaging a curvilinear shell of ETFE pillows, supported by a green oak frame around rectilinear internal spaces and a main oval hall. For a number of organisational reasons Kent County Council decided to bring in the local Lee Evans Architects practice to rethink the project, who started a complete re-design through late 2004 and into 2005. This team led by Matt Hayes re-introduced chestnut as the structural material developing a fourteen beam curved cruck-frame structure, which enabled the re-versioned roof to softly slope from its entrance high point down towards the lower far face.
Inwood Developments were to produce the buildings engineered chestnut, and have since gone on to develop chestnut glulam as part of their suite of chestnut materials, but in 2002 the wood had not been sufficiently tested for its load-bearing and other structural properties. As part of the Shorne Wood project five glulam beams from 18 year old chestnut were therefore dispatched to the Building Research Establishment (BRE) and tested to destruction, revealing both a surprising extra degree of both flexibility and elasticity than had been assumed would result. This gave the required green light for chestnut glulam going into production, the resulting research today publically available on the BRE site. In-Wood’s glulam production has been heading upwards ever since. The architects, Inwood and engineers Faber Maunsell next developed a hinge system for the cruck-frame; designing 32 identically shaped glulam beams, joined by a hinge not unlike those found on pairs of scissors, making it possible to open and close the beams and vary the undulating ridge of the building. Faber Maunsell also provided sixteen different steel connectors, allowing for the frames natural movement, as found in all timber structures.
Read had thought the chestnut would come from Shorne Wood; in the event less than 5% was sourced from there, due to the young age of the coppice stands and the clay soil affecting timber quality. He estimates that the total amount of chestnut used is equivalent to 65 kilometres of 100mm by 25 mm fingerjointed timber with 2 to 3 lorry-loads or kilometres being delivered to Inwood from the country park. The majority came from Kent and its surrounding counties. Read caveats this slightly disappointing result with the information that nearly all the door and window joinery came from oak thinnings from another Kent County Council site; Parkwood, near Appledore.
With the building completed after a forty-week build, Read and the rest of the team moved in. He talks of the buildings organic sensibility “ with the exposed cruck-frame fully expressed in the interior’s foyer and interpretation entrance – as both pleasant as a working environment and a complete hit with the general public, who have also picked up on the overall sustainability message. With a significant budget, £2.3 million, one £1 million each from the Office for the Deputy Prime Minister – now Department of Community and Local Government – and Kent County Council, the whole Visitor Centre also highlights various renewable features; PV’s on the centre’s roof and a 15kw single wind turbine in the car-park.
All this suggests that the local materials agenda is spreading. As referred to in the main piece, Inwood cannot keep pace with demand; and they are aiming to double chestnut production in the next couple of years from the current 1440 cubic metres annually to nearly 3000 cubic metres. This is after a previous doubling over the last two years. Although it is early days, Read tells an intriguing story which demonstrates the potential of where an aspect of this local timber economy may be heading. In May this year, he hosted a visit from foresters in oak-rich Normandy, across the channel. A few months later the two regions are exchanging even more timber, perhaps one day chestnut. It’s only a beginning, but adds another layer to the emerging local materials story.
A version of this piece originally appeared in Green Buildings magazine issue