Blythe Hill House reimagines a 1970s terrace in southeast London, challenging the conventions of the typical rear extension. Rather than a shallow, extruded addition, the project extends deep into the garden, using the plot’s unusual width to create a 14-metre-long structure that reshapes both the plan and the landscape.
A new timber extension runs perpendicular to the rear elevation, forming a sheltered courtyard and creating a series of adaptable rooms. Full-height glazing establishes a strong visual connection to the garden, drawing daylight deep into the plan and allowing the spaces to respond flexibly to the evolving needs of the young family.
The project was developed with a strong emphasis on reducing embodied carbon. With mature trees surrounding the site, traditional deep concrete foundations would have been disruptive and carbon intensive. In response, we adopted screw pile foundations, avoiding extensive excavation and halving the embodied carbon associated with the groundworks. This approach saved over two tonnes of CO₂ – around a quarter of the project’s total emissions.
A lightweight timber frame, hempcrete infill and on-site renewable energy – photovoltaic panels, a battery for electricity storage, and an air source heat pump – further support the project’s environmental ambitions, and contributes to an improvement in EPC rating from D to A. The completed extension achieved a SCORS A rating, demonstrating how structural choices can support low-impact construction without compromising internal space.
“Breaking from the usual infill or extruded approach, this extension utilises the plot’s extra width to create an elongated form, generating a private courtyard and introducing unexpected spatial variety and flexibility within the home,” – says Camilla Parsons, Director at Whittaker Parsons.
Together, the architectural and structural strategies deliver a carefully considered addition that extends the life and performance of the existing house while responding sensitively to its setting.
