Elegant single-storey wraparound extension to a locally-listed detached house within a Conservation Area in South London. Responding to the form of the existing building, the extension steps in plan to create an outdoor room beside the new interiors. The red-brick ‘cogging’ detail that runs around the roof of the existing building is here replicated at the head of the flat roof, a further nod to the heritage of the original house. To keep the carbon costs down, the extension has been designed as a timber frame structure. Existing low-energy underfloor heating systems are extended, while an efficient cooling system ensures a constant supply of fresh air within the new spaces.