Cobalt Place, Surrey Lane

Residential

A development boasting impressive sustainability credentials, using cross laminated timber to make a building with 41% of the embodied carbon of a traditional reinforced concrete design (i.e. 59% less).

Walsh was appointed by client Lendlease as the structural and civil engineers for two residential blocks of five and six storeys.

Initially, Walsh identified either a traditional concrete, or a more sustainable cross-laminated timber (CLT) frame as the two most suitable solutions for the blocks. The CLT panels, however, were able to span up to 5 metres and provided a significant depth advantage over steel or concrete frames.

The pre-fabricated nature of the CLT panels also ensured high speed construction, with a 15 week build period for the structural frame. This improved the project’s sustainable credentials, both environmentally and economically. Waste was kept to a minimum; and it meant improved site safety with a smaller work force needed; less materials stored on site, and fewer structural changes having to be made during the construction process.

In addition, the lightweight properties of CLT meant that transport of the panels to site was easier and they were within the transportable and mobile craneage range of 15 tonnes, with the entire construction requiring just two cranes.

The Cobalt Place project was a key part of a drive by Walsh to develop an industry-leading system of analysing sustainability on environmental and economic. Thanks to the findings which emerged from Cobalt Place it now assesses the life cycle impact of embodied carbon on designs and is being used on several current Walsh projects.

The detailed environmental analysis of Cobalt Place by Walsh determined that the blocks combined were 41% of the embodied carbon of an equivalent RC structure. Putting this into perspective, under the London Borough carbon offset systems, an equivalent saving in CO₂ emissions compared to that achieved on the Cobalt Place development from using a timber frame over an RC one would cost between £3.2 and £4.8million.

Throughout the project, several technical challenges emerged, such as structural scheme for supporting the balconies. The proposed cantilevers for the balconies could not be formed using the CLT. Instead they were formed using a bespoke support framework solution, developed by the design team. This customised solution simplified the onsite construction and connection detailing, and minimised steel tonnage.

In addition to using the embodied carbon assessment tool, Walsh has designed and developed a 4D construction sequencing tool that provides a fully interactive animation enabling the user to view the development from any angle, at any point in time. It can show step-by-step installation of everything right from piles being installed to the building being topped-out. This highlighted the quick build time, a significant saving compared with typical concrete build times.

It has been shortlisted in the Community or Residential Structures category of the 2016 IStructE Structural Engineering Awards.

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Exterior ©Lendlease Cobalt Place 002
Prefab CLT Panels ©Walsh IMG_1514
IMG_4364
Level 1 transfer structure sketch ©Walsh

Key Facts

  • Client: Lendlease
  • Location: Battersea, London
  • Year: 2015
  • Summary:
    Cobalt Place is formed of two residential blocks, providing 104 apartments, and is part of the large Surrey Lane redevelopment in Battersea. Covering 15,000m2, the project also includes a three storey townhouse, a new school and a separate building provided for Salesian monks.

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