Mass timber – the future of sustainable construction

MAIN PICTURE –  The American white oak glulam beams take centre stage in the corner of the new Warner Stand at Lord’s Cricket Ground in London. Photo © Jon Cardwell

Almost 20 years after its first use in the UK cross laminated timber (CLT) is yet to be embraced by many in the wider construction sector. Peter Wilson, architect and director of Timber Design Initiatives Ltd reviews a new publication which aims to demonstrate the effectiveness of modern solid timber technologies such as CLT and glulam.

Almost two decades after cross laminated timber first made its appearance in the UK, it and several of the other modern engineered timber products that have been transforming much of the country’s construction remain, for many in the industry, something of an unknown quantity and to be avoided until they are “more proven”.

Whilst there are several hundred projects now in existence that ably demonstrate the efficacy of modern solid timber technologies, independent, objective information on their various properties and uses has not always been so easy to come by and have often been the source of frustration amongst designers and other potential specifiers.

With the publication of Mass Timber – an introduction to Solid Laminate Timber Systems, this is no longer the case. Written by Dr Robert Hairstans, head of Edinburgh Napier University’s Centre for Offsite Construction and Innovative Structures* and an acknowledged expert in the field of timber engineering, the book explores the different glued and non-glued products available, through a detailed examination of the various manufacturing processes, together with their individual properties and performance characteristics.

In response to the endlessly repeated question as to why these products are not manufactured from UK-grown timber, the book provides a highly informative selection of case studies of research and development work undertaken by Dr Hairstans and other colleagues at Edinburgh Napier University into the potential of the various tree species available from the UK forestry sector to be fabricated into commercially viable solid laminate timber systems and products.

The answer is that they unquestionably can be and there is sufficient resource to do so: what is required is greater confidence in the future market and investment in the necessary manufacturing facilities, both areas in which UK industry has traditionally been deficient.

For those who have used some of the products – whether in glued forms such as cross laminated timber (CLT), glulam or laminated veneer lumber (LVL), or in non-glued variants such as dowel laminated timber (DLT) and nail laminated timber (NLT) and who may feel reasonably knowledgeable on the subject, the book has other surprises in store.

The world of advanced timber technologies and that of solid laminate timber systems is continuously evolving and no more so than in their manufacture from hardwoods, in an industry historically dominated by the use of softwoods.

Why should this be so? First, hardwood production worldwide is forecast to rise as a result of climate change and increased planting and second, the strength relative to weight of hardwoods allows for more slender proportions to be achieved. Further case studies in the book highlight recently completed projects that make exemplary use of cross laminated timber, glulam and laminated veneer lumber fabricated from hardwoods and the potential of these relatively new products and systems to introduce a new dimension to timber design and construction.

Take the Warner Stand at Lord’s Cricket Ground in London, where the structure of the new roof canopy is formed from 11 double tapered glulam beams of up to 23.4 metres in length. Designed by Populous Architects and ARUP Engineers, the beams have been fabricated from American white oak, the first occasion the species has been used on this scale. Doing so was not simply a case of using a hardwood instead of a softwood – the technical challenges are quite different and, in this instance, required extensive research, development and testing to be carried out by the engineers and the manufacturer, Hess Timber.

Caption – The 23.4-metre-long beams stretch across the stand, providing cover for the guests.
Photo © Jon Cardwell

Adhesives that work perfectly well with softwood, for example, could not be absorbed by the white oak due its density, a significant problem for finger-jointed connections but one ultimately successfully solved by the use of a modern melamine adhesive, a solution that would not have been possible a decade ago.

The use of hardwoods in the manufacture of large-scale glulam elements and other solid laminate timber products is relatively new territory in which further research and development will likely to lead to wider commercial production and consequent new architectural and engineering possibilities.

The Warner Stand’s hardwood glulam beams, as well as other projects highlighted in Mass Timber – an introduction to Solid Laminate Timber Systems, have undoubtedly pioneered the way for even more advances in the use of the latest developments in timber technology: time now for new creative design thinking about how these might be used in construction

* (www.cocis.napier.ac.uk)

Peter Wilson is an architect and director of Timber Design Initiatives Ltd, a company specialising in continuing professional education, product and system innovation and demonstration of the use of advanced timber technologies in architecture and construction.


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