Wood: A material for the 21st Century

Materials World magazine
,
13 Oct 2014

Peter Wilson from Edinburgh Napier University, UK, explains how recent technological developments and innovations in timber engineering are helping this natural material stand tall among its rivals. 
Wood has long been regarded as the poor relation in the materials world, a natural product considered by many to be more suited to domestic construction than to large-scale building and civil engineering projects. For others, too, the connections between forest research, wood science and the creation of new construction products have been far from apparent. But this lack of awareness of recent developments in timber design and construction is perhaps more a result of the industry’s focus on its own evolution, rather than on getting the message out to the wider world that wood really is the material of the future.

That last phrase may sound oddly evangelical, but it is simply a statement of fact. True, wood won’t ever entirely replace concrete and steel in large-scale civil engineering projects, but recent technological developments and innovations in timber engineering are inspiring a new wave of creative thinking about the range of situations in which wood can be used successfully. This has been driven in part by widespread environmental concerns together with the implementation of ever-higher targets for carbon emission reductions, and also by legislative restrictions designed to prevent the importation of the (often illegally harvested) tropical hardwoods, previously used for external purposes, such as canal lock gates. The search for alternatives to imports and for ways of expanding the use of locally grown material with consequent value added for the domestic forest resource has become increasingly important. Over the past two decades, considerable advances have been made in both wood science and timber engineering.

Such areas are addressed at events and conferences that bring together industry academics, researchers, engineers and manufacturers all over the world to discuss the latest developments and ideas in both of these areas. This demonstrates the vibrant international discourse currently underway on how we can encourage better and increased use of wood in construction across all parts of the globe. But the world is not changed by theory alone. It is realised and tested through practical application. In this respect, a number of connected themes can be identified as game-changers over the last 20 years – the evolution of large-scale engineered timber plate elements and the consequent emergence of new thinking on how tall buildings can be constructed in inner city areas is just one of these interconnections.

Construction at speed

The 1990s saw the first commercial applications of a product called cross-laminated timber, also widely referred to as CLT or X-Lam. The benefits of the product are many – not the least its capacity for highly accurate offsite manufacture, but also its ability to be produced in large dimensions. With its two-way spanning structural capacity, it is also a ready means of forming floors, walls and roofs extremely quickly, with very little skilled manpower required. Over the past decade, huge numbers of new schools have been built in the UK using this form of construction. Speed of erection, reduced waste and high thermal and airtightness standards are other advantages that have attracted the country’s supermarkets towards building their newest stores in timber.

Significant though these examples may be, the real game-changer has been the application of CLT in the design of tall buildings. First up was the Stadthaus in Hackney’s Murray Grove, by architects Waugh Thistleton and engineers Techniker – a nine-storey apartment block built over a ground-floor masonry plinth. At the time of its construction in 2009, this was deemed to be the world’s tallest timber housing development and it caught the attention of engineers around the globe who, have proceeded to conceive higher and higher timber structures. Techniker kicked things off with conceptual designs for 30-storey timber buildings, but the next practical development took place in Melbourne, where an 11-storey housing block was built. A 14-storey all-timber structure has recently begun in Bergen and a 34-storey apartment building is mooted for completion in Stockholm in 2017.

Across the pond, steel tower architect par excellence, SOM, was re-imagining a 46-storey Chicago tower it designed in the 1960s as if it were made from timber, and conceiving an achievable hybrid means of doing so. This was taking tall timber construction into the heart of the corporate world. Over in Vancouver, Forest Industry and Innovation had commissioned architect Michael Green to produce Tall Wood, a technical appraisal of the capacity to construct commercial buildings of up to 20 storeys from timber. Green has since built the nine-storey Wood Innovation and Design Centre for the University of North British Columbia (now deemed the tallest timber structure in North America), and has published his design for a 30-storey timber tower in Vancouver, a city where the green credentials of new buildings are becoming ever more important.

London leads the way
It is in city building and urban design that the benefits of timber construction are being increasingly accepted, with London leading the way – this in a city that had Building Acts produced in response to the Great Fire of 1666.

Near to the Stadthaus in Murray Grove are several CLT structures. At Whitmore Road, a seven-storey mixed-use development (also by Waugh Thistleton architects) built on the edge of the Regent’s Canal illustrates the structural capabilities of prefabricated timber panels. Meanwhile, Bridport House, an eight-storey residential block built by Karukusevic Carson Architects over a Victorian sewer, demonstrates the value of the material’s lightweight construction compared to traditional technologies. Each of these projects has been so successful (recorded benefits being speed of erection and adjacent tenants experiencing little site noise or waste) that Hackney Council was prepared to consider implementing a timber-first policy, in which any planning application would have to demonstrate why timber was not being proposed as the first choice of construction material. While this idea may prove difficult to pass into local legislation, there is no doubting the mood swing – timber is no longer regarded as a low-value building material and new, dense urban construction is very much the global name of the game.

More could be written about CLT and other variants on prefabricated solid timber panel construction, but the primary area of my own interest in this field is in getting these products into UK manufacture from homegrown timber. At present, the bulk of manufacturers are in central Europe – Austria, southern Germany, Switzerland and Slovenia – and, given these countries’ wealth of forest resources, large-scale investment in plant and excellent products, this is unlikely to change. Recognising the potential of high added-value use for its own forest resource, in 2011 the Scottish Government charged Edinburgh Napier University to get CLT into commercial production in Scotland as soon as possible. Since then, with additional funding support from the European Regional Development Fund, its timber engineers have manufactured panels from six different species (the emphasis being on Sitka spruce, the predominant production species in the UK) and carried out fire and structural tests, as well as market appraisals for this domestic product.

To date, panels made from homegrown timber have been used to form shear walls in the BRE Innovation Park Visitor Centre on the site of the old Ravenscraig steelworks in Motherwell, and in the Commonwealth Games Athletes Village housing in the east end of Glasgow. Currently, discussions are underway with industry investors with a view to establishing a large-scale commercial production facility in central Scotland, and it is hoped this will be up and running in the near future.

Altered states Solid timber is not the only game in town. Major advances have been made in recent years in wood modification, the process by which the cell structure of wood is altered by either chemical or thermal means to create a quite different range of mechanical and physical properties. So much so, that radiata pine, a species considered to have relatively low durability when used in exterior conditions, becomes sufficiently durable following a chemical process known as acetylation. This makes its use in the lining of canals, for example, entirely possible.

Timber, then, is not a secondary construction material – it has become primary and, with every passing day, new and innovative uses are being researched and developed. Now very much in the world of high-tech engineered products, it is a material for the 21st Century and one that has the capacity to transform towns and cities around the globe into greener, healthier and more humane environments. What’s not to like? 

Peter Wilson is an architect and director of the Wood Studio, a specialist timber research centre within Edinburgh Napier University’s Institute for Sustainable Construction. For further information, email pr.wilson@napier.ac.uk