Chart Street is a redevelopment of an existing 1930s masonry warehouse located in Hackney.

Chart House is a redevelopment of an existing 1930s masonry warehouse located in Hackney. Designed by Ian Chalk architects in collaboration with engineers Heyne Tillett Steel, the building has been remodelled into a sustainable and collaborative workplace.
Demonstrating a commitment to retrofit and reuse, once complete, the building will provide expanded studio space for Heyne Tillett Steel’s 130-strong practice. Conceived as a creative working hub, the building reflects the practice’s approach to low-carbon structural design.
The existing four-storey building has been redeveloped to include a new side extension, a new storey on the roof and a new circulation core. A central staircase has also been installed to improve internal circulation.
The new extensions have predominantly been built in CLT and engineered timber. Due to their lightweight material qualities no additional strengthening to the existing structure was required, helping to drive down carbon emissions.
The new roof extension has been designed with a sawtooth Northlight which will help to reduce solar gain. Formed from CLT panels and high-strength BalBuche LVL beams, the extension will create extended open plan office space for presentations and collective activity. The heating and ventilation system will be electric-powered, and each floor will feature openable windows to allow for natural heating and cooling.

One of the first key decisions was to reuse and extend the building rather than demolishing. This saved a significant amount of embodied carbon over a new-build option and gave the 90-year-old warehouse 60 more years of life, reincarnated as an office.

The building has a practical and “analogue” approach to circularity. Repairs to fabric were done only for structural repairs, imperfections were celebrated, and new finishes were used sparingly. This minimises material use and maximises future adaptability. Keeping the structure and services exposed also allows for repairs, upgrades and alterations to be made with minimal waste. The new structure is mainly mass timber, in a panellised construction with exposed structure and reversible connections.

The building has windows on four sides to provide daylight and ventilation, and heat recovery systems in the lower ground floors. The new CLT roof extension forms an efficient warm lid, with sawtooth windows facing north to maximise daylight. The new CLT side extension shields the south elevation from solar gain with opaque windows to allow for ventilation. The decision not to insulate the existing masonry walls was a balance between the embodied carbon of all the associated components and the potential carbon saved through heat retention over the operation life of the components.

Laura Batty, Associate – Technical Research & Sustainability, Heyne Tillett Steel