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Cross Laminated Timber – The Benefits in Transport Terms

Cross Laminated Timber – The Benefits in Transport Terms

Want to reduce construction traffic by 75%? Maryam Shakiba and Matt Harris discuss their findings on the benefits of CLT.

Markides Associates have been appointed by Landsec to assist in the planning and design for a large commercial development on the South Bank, in the London Borough of Southwark.

As part of Landsec’s commitment to sustainable design and innovation, the two commercial buildings are being designed using a combination of the partial reuse of the existing structure for one of the buildings and the use of a hybrid/Cross Laminated Timber (CLT) structure for the other. Through this approach, the carbon emissions associated with the redevelopment, from all aspects of development, will be significantly reduced compared to a traditional office site redevelopment in the City.  

Cross Laminated Timber – CLT – is a key element to the fabric of both buildings. CLT is a structural, prefabricated panel used to form a wide range of structures. Layers of lumbar boards are stacked crosswise at 90-degree angles and glued into place, reducing the movement of the wood, and ensuring that CLT more than meets standards required by modern building materials. CLT use has a wide range of advantages, not least the potential for reducing the construction vehicle trips associated with the redevelopment.

As part of our work with Landsec, we undertook a detailed exercise analysing the difference in construction vehicle trips generated by this hybrid build versus traditional build methods. The scenarios considered the partial demolition and hybrid build proposal put forward by Landsec for the site alongside the full demolition with traditional build scenario that could otherwise have been the case.  

In transport terms, the benefit of a hybrid build is seen in the significant reduction in construction trips required through the build process. The reduction in construction trips is the result of two main features of CLT material:

  • CLT floorplates are lighter, meaning more plates can be carried per truck; 100m3 of CLT can be carried per truck, compared to 6m3 of concrete.
  • No concrete or wet trade is required, entirely eliminating the main trip generator in traditional build methods.


Hybrid build method with CLT generates just over 100 vehicles in the construction phaseFor the same site, a traditional build method generates over 400 vehicles during the construction phase

In the case of this development, the hybrid build construction phase was estimated to generate approximately 25% of the construction trips that a traditional build would have generated. Over the entire construction period the partial demolition/hybrid build scenario was forecast to generate approximately 2,500 fewer trips than a full demolition/traditional build. This significant reduction in construction traffic allowed Landsec to clearly demonstrate to the London Borough of Southwark its commitment to sustainable design and the reduction of carbon emissions associated with the redevelopment.

Whilst the use of CLT as a material has other implications which the development industry in the UK is still trying to fully understand, particularly post Grenfell, this study clearly demonstrates the benefits of CLT and partial demolition proposals with the potential for significant transport and traffic benefits. With the prospect of reducing construction vehicle trips by up to 75%, it will be interesting to see how CLT evolves over the next few years, if it can gain traction and ease wider concerns surrounding its use, it will be undoubtedly deliver positive outcomes for developers, particularly in sites that are sensitive to construction traffic impacts.

A graph showing the difference in totals. Hybrid methods cut traffic by 75%

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