Can the Built Environment Be Pre-Manufactured From Mass Timber?
Globally, the production of mass timber systems is increasing exponentially, driven largely by the need for more sustainable ways of delivering the built environment. Dr Robert Hairstans, Associate Professor at Edinburgh Napier University and Head of the Centre for Offsite Construction + Innovative Structures explains further.
Coinciding with this is also a worldwide shift to more construction activities being carried out offsite in factory environments, given the need for improved levels of construction productivity combined with technological advances that are being made, both mechanically and digitally. Mass timber slab and beam components can be brought together and combined with other materials offsite to form modular or volumetric units capable of being enhanced to a high level of factory finish which equate to turnkey solutions.
Edinburgh Napier University has undertaken extensive research on the various forms of mass timber products for such applications, work that has involved pioneering research on the integration of UK timber fibre into various forms of solid laminate timber system including cross-laminated timber (CLT), dowel-lam (DLT or Brettstapel) and nail-lam (NLT) and which has resulted in the their fabrication, structural testing and follow-on integration into live projects.
Growth and Acceptance
The mass timber family of products consists of various form of solid laminate timber systems. However, it is the panelised or slab forms of mass timber, primarily CLT, that have particularly ‘moved the needle’ for use and application of timber in construction given their capability to form whole building envelopes, often in combination with mass timber beam products (glue-laminated timber and laminated veneer lumber) and other construction materials in hybrid forms.
The exponential growth in use of CLT is driven not only by the environmental credentials of timber as a product, but also by the structural attributes of the panels ascertained from this process that allow timber to be used in building applications beyond normal limitations. Once fabricated, the mass timber product is normally cut to the required shape and size for the end application via CNC (computer numeric control) saws which have the capability of cutting in almost any direction with the precision necessary to form openings, services voids or acoustic performance-enhancing profiles.
To streamline these processes, the CNC operations will be linked to computer aided design (CAD) and computer aided manufacture (CAM) software. It is worth noting that this approach can also be utilised on NLT fabricated with aluminium nails. These offsite manufactured mass timber products can then either be shipped direct to site or formed into offsite volumetric modules that can be taken to a high level of finish with windows, doors, external cladding and internal linings and services included. Carbon Dynamic a company based in the Scottish Highlands, are currently deploying this approach in the delivery of student accommodation for the Dyson Institute for Technology.
Mass Timber Requires New Design Thinking
The utilisation of mass timber products requires a change in design thinking particularly when the products are to be further formed to create full volumetric units with an enhanced level of finish. Designers need to take cognisance of the capabilities of the mass timber manufacturing process (dimensional compatibility, CNC cutting and routing capability) and follow-on production activities (factory lifting, allowable space, available tools and equipment) to create the volumetric system. In addition, the logistical arrangements, from both a transport and site access perspective, need to be taken in to account.
Information and communication technology (ICT) system integration; understanding the full parameters of design for manufacture and assembly (DfMA) as well as disassembly (DfMA+D) and ensuring an early design freeze are therefore of high importance in adding more value in the factory and ensuring successful project delivery. DfMA+D takes cognisance of end of life or change of use, such that the building components are demountable in the future for reconfiguration or alternative applications.
Going forward, digitisation and the emergence of integrated BIM platforms that facilitate the inter-operability of software utilised during each stage of the mass timber production process can enhance the level of information that resides within the built asset with a digital thread. In theory, this can provide the capability of tracing the source material back to the forest and thereby inform the product’s overall environmental credentials. The use of virtual reality and augmented reality (VR/AR) will facilitate knowledge exchange for upskilling and early integration across the project team, as well as client and customer understanding for improved decision-making. In-situ, the performance of the unit and its interactions with its users can be monitored, creating a feedback loop for future product optimisation or maintenance.
Advantages and Barriers
Offsite massive timber systems can offer considerable advantages over more traditional forms of construction, particularly when utilising the local timber resource. Responsibly sourced timber has inherent environmental credentials, given that it sequestrates carbon. Prolonging this sequestration in energy-efficient buildings close to sources that conserve energy can help reduce the environment impact of construction. This is fundamentally important, given that buildings account for approximately half of all our extracted materials and energy consumption and around one third of our water consumption. In addition to this, a localised supply chain can reduce transport emissions as well as provide jobs, stimulating wealth creation – hence why Edinburgh Napier University has pioneered work to integrate UK timber fibre into mass timber products. Combining economic and environmental prosperity in this manner and ensuring the responsible management of resource during the manufacture and useful life phases of a building highlights the efficacy of mass timber usage within the paradigm of a Circular Economy.
The social, economic and environmental value of utilising mass timber forms of construction therefore need to be considered during the specification process. Specifying products for a project on material cost alone fails to consider the wider benefits of mass timber and, as a result, other materials and systems can be inaccurately deemed to be more competitive. Mass timber construction has, for example, been demonstrated to reduce construction time on projects by up to 20% when compared to more traditional methods, a factor that can be of particular relevance when the time taken to building sign-off impacts upon the return on investment. Evidence is also emerging to suggest that mass timber buildings offer health advantages by having a positive impact on the stress levels of occupants, an additional factor that can, for example, result in improvements in educational attainment in schools, improvements in business output and assist with patient recovery periods in care units.
There are, however, barriers to uptake, with a lack understanding of the benefits to such methods of construction combined with sectoral resistance to change often impinging upon progress. Manufacturing mass timber at scale and enhancing it further in an offsite environment does normally require high levels of capital investment, thus necessitating a pipeline of work to ensure an economic return. Given that this is the case, collaborative partnerships between industry, government agency, trade organisation and academia are important when bringing mass timber products to market. These types of collaboration have the ability to stimulate the market by means of showcasing and disseminating information, ensuring system compatibility within the regional regulatory context and, importantly, reducing the associated investment risk through the use of public funds to underpin the process.
Edinburgh Napier University has participated extensively in such activities including the first commercial production and pilot project application of CLT from UK resource as well as providing research and innovation support to the CCG Construction Group in the construction of the tallest building in Scotland formed from CLT. In order to address client scepticism, however, future work is still required to fully demonstrate the economic case for mass timber and to create improved levels of guidance for DfMA+D approaches - and combinations of approaches – that ensure value return is maximised for the given circumstance. Continued evaluation and reporting utilising digital data acquisition techniques will help to build this evidence base and demonstrate the true value proposition of mass timber construction.
More on Mass Timber
Dr Robert Hairstans undertakes research, innovation and knowledge exchange activities in order to deliver construction technologies for tomorrow’s communities within a circular economy. His recent publication Mass Timber – an introduction to Solid Laminate Timber Systems (available from Arcamedia, https://www.arcamedia.co.uk/) is considered to be a strategic milestone towards full commercial production of mass timber in the UK.
Robert will also be presenting at Solid Wood Solutions held at the Oculus, University of Warwick 5 July.
As engineered timber technology is one of the fastest growing offsite methods of construction, this event is designed to inspire through innovation. The event will consist of a bespoke exhibition of circa 25-30 companies from within the CLT, LVL and glulam technology sectors, plus complementary solutions such as SIPS and cladding/fenestration solutions with a conference of approximately 200 delegates.
For more information visit: www.solidwoodsolutions.co.uk
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