Sussex House by Wilkinson King Architects
A commercial factory manufacturing cross-laminated timber (CLT) from Scottish timber is now a “serious proposition”, according to Peter Wilson, who leads the Wood Studio at Napier University.
Wilson, who has been carrying out research aimed at raising the value of Scotland’s forestry industry for the past 10 years, says there are “two companies that are close to investing in cross laminated timber”.
He expects a decision on whether a factory is built to be made “this side of Easter” and said that he would be “broken hearted” if production of Scottish CLT manufactured from Scottish timber did not happen in the next two years.
After investment is confirmed, it could take roughly 18 months to find a site, build a factory and order machines, before the manufacture of CLT from timber grown in Scotland can begin.
Waingels College by Sheppard Robson. Image by Hufton and Crow
Fact file: Cross-laminated timber
Cross-laminated timber (CLT), is an engineered panel made from layers of spruce arranged crosswise and glued. It has high strength, dimensional stability and offers the speed and cost benefits of offsite construction. It even performs well when exposed to fire – the charring on the outer layer acts as an intumescent coating.
In the UK, CLT has so far been used for a small but steadily rising number of projects, including the nine-storey Stadthaus apartment block in Hackney, briefly the tallest such structure in the world. Lend Lease is also using CLT to build half the 3,000 homes planned for the Elephant & Castle.
A CLT factory would be the culmination of several years of practical research and feasibility studies carried out at Napier.
This included a survey of Forestry Commission-managed land to determine if there will be enough material produced over the next 25 years to sustain an industrial plant, and a survey of demand. Both indicated that a CLT plant was a feasible proposition.
Following the surveys test panels were manufactured in Inverness that have been tested for strength, stiffness and structural integrity. These test panels have met the European standards required, setting the foundations for industrial manufacture to begin.
At present there are no British manufacturers of CLT, meaning that contractors wanting to specify the material have to seek suppliers from continental Europe or Scandinavia, increasing its embodied carbon and subjecting projects to fluctuating costs.
In general, most timber used in the UK is imported – the UK is the world’s third largest net importer behind China and Japan – a statistic that the Grown in Britain campaign is currently trying to change.
Britain has the same species as mainland Europe, but trees grow faster here so the timber is not as strong in its untreated state. However, with thermal modification, hardwoods such as ash and sycamore can become suitable for a wider variety of uses, potentially creating a new market for the trees cut down due to ash dieback.
Steve Cook, principal sustainable development manager at Willmott Dixon, told Construction Manager: “At the moment, all CLT is imported from mainland Europe, but if the concept can be proven it could pave the way for investment in a British manufacturing plant.”
CLT’s stock as a building material in the UK has risen in the past four years and its manufacture in Scotland would potentially have many benefits to the construction industry: it could create more cost certainty around the material, reduce transport costs, boast local employment and raise the value of Scotland’s forestry.
