Overview
16 Chart Street is a redevelopment of an existing 1930s masonry warehouse located in Hoxton, to create new headquarters for Heyne Tillett Steel.
The four-story building has been repurposed and the area increased to include a new side extension, an additional storey on the roof and a new central staircase. Conceived as a workshop and studio space, the new floor level has been designed to promote collaboration featuring a flexible, column free space with four rows of 10m long, north-light, windows maximizing indirect light.
B&K Structures supplied and installed the cross laminated timber, glulam and BauBuche beams, and the elements of structural steel, to support the refurbishment of the existing three storey building into new commercial space, with the addition of a one storey CLT roof extension and external structural staircase.
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Our design team provided the temporary works for the propping of the structure during installation and worked very closely with HTS to contribute to the design and development of their connection details. The CLT has been left exposed throughout the building, mimicking the exposed masonry finishes of the original building. With exposed connections and articulation of joints, when seen collectively this forms a pleasing variation of material intersections between the old and the new, allowing the spaces to have their own character whilst retaining a familiarity throughout.
The end result being a considered and didactic expression of the building’s construction; expressed panel joints, exposed lamellas and undisguised connections all demonstrating the buildings sequencing. With embodied carbon calculations in mind, the scheme was able to reuse most of the existing building and incorporate CLT to help reduce the upfront embodied carbon of the building.
The extensions were predominantly built with CLT and engineered timber, provided by Stora Enso, lowering embodied carbon and speeding up construction. Through low-carbon structural design and the reuse of the existing structure, the project has achieved the LETI and RIBA 2030 targets for embodied carbon.
Installation
Main works were the top-level roof extension, where BKS installed the CLT floor, walls and roof and propped the walls and steelwork gradually throughout the erection phase. Challenges were presented due to the covid pandemic and weather issues, but the final result is a sustainable and stunning scheme. Despite reduced site deliveries due to minimal space to lay materials, the roof extension frame was erected in three weeks and the side erection was erected in one week due to the strong collaborative approach between BKS, HTS and Conamar. The temporary propping design and installation strategy was complex due to the unusual geometry and high pitch of the roof and the sequencing required close collaboration with HTS’ structural engineers but ensured a stunning final result.
BKS were responsible for the erection of the steel frame for the stair core and side extension, which involved a challenging erection phase due to the logistics of the long and slender steel members and limited space. The timber side extension included CLT walls and floors, with Glulam support beams at every level.
A key aspect was the inclusion of the BauBuche laminated veneer lumber beams, which are manufactured using Beech. The hardwood members provided additional stiffness and slimmer beam dimensions, as well as a unique architectural feature.
While the installation of the Beech was challenging due to the susceptibility of the timber to water damage, the BKS team developed a project-specific moisture control plan and worked closely with Conamar to ensure that, on delivery, the timber was protected before and during the installation stage until the roof was sealed.
Sustainability
BKS were proud to contribute to a project supporting the circular economy through the use of retrofit and refurbishment, and all timber was sustainably sourced with PEFC Chain of Custody certification.
The total volume of the CLT, Glulam and LVL delivered was 194.71m³ (PEFC and 70% PEFC) and the CLT and Glulam timber used on this project has captured 145 tonnes of CO2e. The responsible management of European PEFC forests ensures that the timber used on this project was completely replaced by new growth in just 1 hour, 13 minutes and 46 seconds.
