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THE
FLIMWELL WOODLAND ENTERPRISE CENTRE MODULAR GRIDSHELL
Across
the other side of Sussex, almost dabbling its toes into the Kent
borderline, is the Wood Enterprise Centre. The Centre is host
to a structure which has adapted the gridshell form, and although
not a pure gridshell can be described as including a modular gridshell
roof. If it isn’t a conventional gridshell Flimwell includes
a number of characteristics which can, arguably, make it part
of the gridshell fold.
 
Image
Woodland Enterprises Limited
Seven
years since the project was conceived, the Feilden Clegg building
went up in 2000, with its adapted modular gridshell roof, cladding,
walls and flooring, all using chestnut. Right in the heart of
the South East’s once extensive chestnut region, a principal
aim has been to demonstrate that chestnut can again be employed
as a contemporary material. As with the Weald and Downland gridshell
building it is an attempt to embed contemporary use in the midst
of a traditional rural context. Unlike the Downland gridshell
however, the project has been generated by the forestry, and rural
industry, rather than building and architecture.
By
the early nineties, with the withering of the chestnuts industries,
outpaced by cheap softwoods, it became clear to those working
in the region that if anything of the economy was to survive,
new uses for the wood would need to be found, epecially as chestnut
is such a predominant wood in the clayey Weald of the South East,
where there are19,000 hectares of trees. There is an annual excess
of timber of half a million tonnes a year, and each year, the
core tree capital grows another 100,000 tonnes of potential timber.
If this amount is used in a year then the harvested amount doesn't
actually affect the central reserve of core woodlands. Fencing
and outdoor materials takes up the best of the coppiced tree,
leaving lower-grade material, which hitherto could not be used
for primary uses because of the irregularities caused by knots,
and uneven surfaces. Up until recently it has gone to be pulped
as wastewood. But at the Woodland Centre, a whole new variety
of uses are being created.
Before
the Woodland Centre was mooted, regional foresters and timber
engineers had long felt that if a project could be put together
which demonstrated that if chestnut was a strong enough material
to pass various structural tests, it could once again be re-introduced
to the building and construction market as a home-grown and therefore
far more sustainable wood to utilise. Aware of the developments
in timber and glue technologies, the engineers were confident
that if these were applied to chestnut interesting results would
follow. Furthermore, if this could be demonstrated by an innovative
building – a living example of how the wood could be used,
and packed with examples of designs, including furniture, and
other uses the wood could be put to - this could only help the
future of the industry.
 
Image
Woodland Enterprises Limited
There
had already been a number of experiments using coppiced chestnut.
Some of the buildings at the local farm, where one of the woodland
partners worked, had been replaced using chestnut. Subsequently,
the roof of a local sawmill was rebuilt using the wood, after
a successful test hanging weights from beams which demonstrated
that the timber would be strong enough to support the roofing.
It was also known that there was a strong sustainable argument
for this resurrection of the wood as a commercial material.
Those
involved felt sure chestnut would measure up, but the wood needed
to be comprehensively and formally tested. With a strand of EU
money, called Life funding, and wood donated by a local sawmill,
the Building Research Establishment (BRE) were brought in to the
research picture. Firstly, English oak, (in 1995/6) and then the
chestnut, (in 1997) were examined for their structural properties,
and stress strengths. BRE's research demonstrated that chestnut
was indeed both safe and strong. What emerged from testing strength,
stress, and durability capacities to sections of both chestnut
and oak, was that much less hardwood was needed compared to softwood,
to support or carry specific weightloads. If a building uses smaller
sections, it will use less wood, and that wood immediately gains
a competitive edge. This was good news for chestnut, as was the
fact that the results have made their way into the review of British
Standards for Temperate Hardwoods (BRE Digest 445) which will
lead to the revision of BS 5268: Part 2. The implication was that
chestnut could be considered for use by architects and the building
industry. It also meant that research shows that the best of the
low-grade timber could be used for building. With deformations
removed, remaining timber could be cut into small 350-50Omm sections,
and using finger jointing technology and, as in Weald and Downland,
Collano polyurethane glues, reconstructed into long slats - up
to 30 feet - from which the modular roofing sections could be
created. Structural engineers, armed with the materials research
would now be able to model large-scale structures, such as modular
gridshells, using the chestnut.
 
Image
Woodland Enterprises Limited
Out
of this positive research exercise a part-private, part-public
company, Woodland Enterprises Ltd, was set up to develop ways
to first steer, and then exploit the research alongside other
concurrent initiatives to breathe life back into woodland industries.
Now,
the idea of a complete building - constructed from chestnut -
could be envisaged. Woodland Enterprises began to look at this
as a serious option. The concept of an actual physical woodland
visitor centre had been in the ether for a while, but with the
structural and materials research in, a feasibility study was
commissioned. Once completed, this again showed the potential
for developing a market for locally produced hardwoods, and chestnut
specifically, and a bid from Woodland Enterprise was, in 1996,
one of only six to receive a grant of one million pounds. From
there a competition produced an imaginative entry from Feilden
Clegg, (these days, Feilden Clegg Bradley), chosen because of
how Woodland Enterprise envisaged trees from the locale being
integrated into the building plan. After some to-ing and fro-ing
Feilden Clegg adapted their plans to concentrate a chestnut as
the building’s primary material. The project evolved into
a working woodland centre, aimed at providing training, work and
accessiblity to the woodland industries community. Feilden Clegg
was able to develop a new building with a modular roof, rather
than a purely gridshell roof as the original brief required.
The benefits of the research began to kick in. Feilden Clegg's
rejigged building plan integrated slats as part of the modular
gridshell roofing structure. For these, chestnut was cut into
short 28mm x 75mrn sections and sent off to Newcastle to be remoulded
into the 10m lengths, which could then be put together as the
gridshell slats for the modular bays - modelled by Brighton based
structural engineers, Atelier One. The chestnut used was freshly
felled greenwood, which meant it was partially dry though retaining
high moisture. This meant that less washing and preparation was
required before drying, producing a much more stable timber. The
suppliers were a local, Kent based Woodland Trust coppice, and
a Sussex-based chestnut forester, Richard Cope. Even If obtaining
the supply was relatively straight forward, certain difficulties
ensued with the joiners and industrial carpenters inexperienced
in working with the hardwood. Indeed what became, was the need
to introduce industrial carpentry and finger-jointers to the special
requirements by hand, as it is a difficult and unknown material
for those used to softwood. Specific machinery designed for hardwood,
as softwood-centred technology is not entirely suitable.
When
the wood arrived, it did so in varying conditions and quality.
The key to ensuring that the chestnut is good enough to be used
is through the initial selection process, what must be done by
a skilled eye, and experienced assessor. The chestnut research
consultant, and timber engineer, Nigel Bradon, has developed this
to a fine art, identifying where the slope of the grain is too
steep, or the proportion of knots too heavy, both of which can
lead to failures. Once identified, the potential defects are removed,
and visual timber grading is applied for future usage, and then
the timber is sawn into 75mm by 25mm sections.
The
building, which sits off the edge of the A21, south of Tunbridge
Wells, deep in dense Weald woodland, is a compact and attractive
mid-sized structure, fitting well amongst the surrounding trees.
The large-span modular gridshell carries five bays, the sawn and
fingerjointed laths, bolted together, comprising the barrel vaulted
arches. The curve of these arches is slightly eccentric, rather
than symmetrical. The five bays were constructed on-site by Cowley's,
the timber carpenters. These modular sections can be constructed
anywhere, in prefabricated units in a factory, and transported
to the prospective site.
 
Image
Woodland Enterprises Limited
Feilden
Clegg have declared themselves pleased with how the chestnut has
performed from the sustainable angle; it is durable, and does
not need chemical preservatives. Beside the chestnut, the building's
main environmental features include its mineral wool insulation,
making it a low-energy building. Roof lights provide the upper
floor with considerable natural lighting. The aim is to develop
a wood-fired heating system, from excess woodwaste thrown out
by the site's separately owned and operated sawmill, which should
provide enough heat for all of the prospective buildings. The
foundations are concrete - unavoidable because of the Weald's
clayey ground soil.
This
said, the principal sustainable innovation is in bringing chestnut
into the environmental building equation. The centre demonstrates
how chestnut and other hardwoods can be used in mid-sized structures,
and as building components, all locally sourced from across the
South East. Where before the only obvious options have been softwoods,
and/or tropical timber, Flimwell shows that there is a real alternative.
Costwise, the structure is coming in at around £500 per
square metre, compared with rock-bottom steel and concrete costs
of £350. While this is a significant difference, in environmental
terms there is investment going into both the regional environment
and the local economy. This may not be persuasive for smaller
buildings, but as far as mid-sized buildings are concerned it
does look potentially competitive. Set against softwoods, and
due to the implementation of tougher building regulations, chestnut
could well become an attractive option.
The
viability of chestnut as a building materials is demonstrated
in Woodland Enterprises' plans. They are intending to set up production
within the Centre's grounds, and the next proposed building is
a factory, which could prefabricate the modular sections and other
hardwood building components. As such, it provides a persuasive
alternative option to the main new choice being developed for
low-grade woods; its use as wood fuel energy. If fuel is a high
volume industry, by contrast the Woodland Centre chestnut initiative
employs a value-added approach to a low-value material.
Image
Woodland Enterprises Limited
Whereas
regional building requirements are considered, both for mid-size
and domestic buildings, there seems to be considerable scope for
growing a rejuvenated chestnut coppice timber industry. With the
arrival of new building regulations, whether you're mainstream
or at the margins of building, the use of wood, already enjoying
a national resurgence, will likely increase. Major housing developers
are already reintroducing timber, including Wimpey, Westbury,
Laing, and Wilcon. But a main difference with previous timber
industry growth-spurts is its use in low-rise medium-size buildings,
of which there are about 15% average across England, including
hotels, nursing homes, community-centres and commercial and leisure
centres. Here, large-span structures are clearly an obvious option,
and are one of the markets being eyed-up by the Flimwell Woodland
Enterprise. The other primary point is the sustainable sourcing
of local wood.
David
Saunders, the Enterprise Centre’s manager, believes that
around 5 hectares of chestnut would provide enough wood “to
grow a new building every year," If Saunders is right about
his back of the envelope calculations - and there is no reason
he isn't - there are 5 tonnes per hectare of chestnut growing
each year. Thus, 15 tonnes would be enough to grow another Flimwell.
An annual 100,000 tonnes of chestnut could provide the core of
many, many, mid-sized and other buildings for the region, as well
as a versatile variety of other applications. These are provocative
figures to be considered by other regions - within their contexts
– when contemplating how to regenerate rural economies.
It is early days, but through wood and glue technology, Flimwell
has become a temple to the chestnut for aficionados of the tree,
and a laboratory for possible woodland futures.
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