The Jerwood Gridshell at the Weald and Downland Open Air Museum, a 21st century timber framed workshop for restoring and conserving the timber frames of historic buildings, is an appropriate venue for a conference on timber, and around 120 architects and specifiers gathered there on June 27 for ‘Time of Timber’. Sponsored by wood. for good, the Happold Trust and German timber engineering company Merk, the conference was aimed at raising awareness among architects and specifiers of the possibilities of timber.
The speakers, who included architect Edward Cullinan who designed the gridshell, treated the audience to a showcase of timber in construction, from small projects such as apartments in France to the grand scale of Expo 2000 in Hannover.
Torbjorn Birgersson of Moelven outlined the range of opportunities offered by glulam.
“Glulam has almost unlimited possibilities,” he said. Its high strength/weight ratio makes it ideal for long spans, it has good shape stability, its fire resistance can be as high as 40mm per hour, and it has a long life in a chemically aggressive environment.
Peter Ross, associate director of Arup, warned architects that they may be called upon to justify the cost of using timber. When doing this they should highlight the “extreme benefits” of timber, such as the aesthetic appeal, its insulation properties and its sustainability. Also, timber could be used in such a way that money could be saved on finishes.
Andrew Holloway, director of the Green Oak Carpentry Company, which provided the joinery for the gridshell, urged a more collaborative approach when using timber in construction.
“The carpenter as a specialist should be more involved in construction and more involved in the design at an earlier stage,” he said.
Limited training
Dr Peter Bonfield, director of the BRE‘s Centre for Timber Technology and Construction, pointed out that each year around 9 million m3 of timber are used in construction in the UK, yet architects “don’t spend much time thinking about it or being trained in it”.
One of the challenges facing timber processors was how to convert trees into consistent, reliable and high performance products required in construction and, to achieve this, the processing sector had become very technologically advanced.
It was also important that the timber industry listened to the client’s needs. This had been done in cases such as wood and steel rafters which enabled services to be run through.
Some of these technological advances had been seen in lamella roofs, Christopher Mettem, TRADA‘s chief research engineer, told the audience.
The Jerwood Gridshell is a lamella construction and Mr Mettem said the method was enjoying a “fruitful revival”.
Lamella roofs were being considered for “further exciting projects that are still under wraps”, he said, but greater efforts needed to be made to promote laminated European timbers other than spruce. British-grown Douglas fir, larch and Scots pine would be “preferable to laminating sitka spruce, which has plenty of other outlet opportunities”.
A lamella roof was chosen for the Hounslow East Underground station, involving engineer Buro Happold. Senior engineer Ken Jones said that “from the outset, timber was the preferred material” but London Underground had to be convinced of the longevity and robustness of the design.
David Bills, director-general of the Forestry Commission, spoke on the use of certification as a marketing tool. “I know of no other building material that can compete with wood’s benefits,” he said.
Illegal logging continued, but the government had a commitment to sourcing timber from certified sources and, as a major importer of timber, the UK had a responsibility to combat illegal logging.
While Mr Bills said it would become easier for architects to verify the source of timber, he urged NGOs to be pragmatic about the supply situation.
“What if the wood that is fit for purpose is not available in a certified form? Do we use plastics?” he asked. “NGOs need to be pragmatic; we need to build capacity between certification and wood coming on the market. The more people recognise its importance, the more certified timber will come onto the market.”
Peter Davey, editor of The Architectural Review, acknowledged that the biodiversity of forests must be preserved and suggested the way forward was through adding value and “radical engineering”.
“Wood is the only sustainable building material,” said Mr Davey. “It is the only one, if sustainably managed, that can help the planet. We have a duty to use it with architectural invention and imagination.”
