Since our inception in 2007 our practice and staff numbers have grown steadily, and in early 2017 we found that we’d outgrown our existing office and needed new space for our burgeoning team. We wanted a studio which embodies the culture and values of the business, reflecting our approach to low-carbon design, our commitment to retrofit, reuse and expressive structure, and our culture of continuous learning.
Following an extensive search we found 16 Chart Street, an existing masonry warehouse in Hoxton and, with a robust structural frame, generous floorplates, exposed structural features and scope to extend, the building presented an ideal opportunity for us to act as both structural engineer and tenant and create a dynamic office which perfectly suits our needs as a practice.
Often our first move on refurbishment projects, we carried out extensive investigations into the structure and foundations using archive drawings, maps and surveys. Understanding the history and character of the existing building allowed us to understand its full potential for reuse, ultimately reducing the need to intervene and hence embodied energy costs.
Once investigations were complete, we worked with Ian Chalk Architects to develop a design incorporating a rooftop extension providing a large, open space for collective interactions and events. As a practice we recognise the value that knowledge sharing and continuous learning brings to our projects, and so host weekly technical meetings as well as a rolling programme of project reviews, webinars and presentations. Constructed from cross-laminated timber panels, the new floor level has been designed for collaboration and creativity, featuring flexible, column free space and 10m long northlight windows installed within the distinctive sawtooth roof. When designing with timber exposed connections and articulation of joints need careful consideration, and so we essentially think of this as structural ‘joinery’. In collaboration with the architects, we carried out extensive benchmarking and research into the visual grade and strength of the timber elements. Hard wood BauBuche LVL beams were chosen to support the northlights and CLT panels, providing the extra strength and stiffness to reduce the depth and therefore maximise the rooflight openings.
Elsewhere the floor of the rooftop extension comprises a hybrid steel and CLT frame, opening up the existing structure to create open plan working areas, collaborative neighbourhoods and break out spaces. To the side of the existing building, the team designed a lightweight CLT extension, complementing the new roof structure and creating light-filled space for meeting rooms, a new stairwell and a covered entrance to the building.
Through the emergence of the COVID-19 pandemic, we have seen a renewed focus on healthy workspaces with high environmental qualities. This shift in workplace design has allowed us to pause and reconsider the building’s desirability post-pandemic. With this in mind we have increased the levels of natural ventilation, allowing clean air to flow through the building, introduced isolated quiet booths for virtual calls and open-plan meetings rooms, as well as created storage for up to 60 bicycles, allowing more of our staff to choose healthier modes of transport.
To measure and accurately report the building’s environmental performance we worked alongside KLH Sustainability throughout both the design and construction phases. The total embodied carbon for the structure at Chart Street is 171kgC02e/m2, meaning the building outperforms the RIBA, LETI and IStructE targets. This has been achieved in part by retaining 86% of the existing structure, reducing demolition and material waste while adding another 60+ years of design life. Additionally, over half of the new structure is built in timber, an inherently renewable and sustainable material that locks carbon into the building throughout its lifetime.
Working with KLH has also allowed us to measure the carbon input from other disciplines such as architecture and MEP and provide a whole life and operational carbon assessment. This measures at 614tC02e for whole life and 728tC02e for operational, both of which fall shy of the industry’s carbon targets. These findings highlight the need for a truly holistic approach to carbon measurement and the need to embed highly efficient energy strategies into reused buildings, something which will become ever more important in the context of the climate emergency.
Chart Street is now complete and, following the latest government guidance on Coronavirus restrictions, is use by our practice.
Photography by Edmund Sumner