Nutley Terrace by Belsize Architects comprises two townhouses on a large brownfield site in a conservation area in Hampstead, north London. A stepped profile is designed to mediate between an adjacent six-storey residential block and neighbouring Edwardian houses. Intended to take advantage of southerly views cross London, the living and entertaining spaces are located on the upper floors, with the bedrooms and other private areas beneath.
The front elevation is primarily clad in Iroko timber at ground level. Bavarian Jura beige limestone with a sandblasted and brushed finish is employed on the upper floors. Laid vertically in three different lengths, the narrow stone slabs follow the building’s gentle curves and provide visual interest. Staffordhire blue brick is used on the rear elevation. The roofs are flat and include a green roof, as well as a terrace paved in light grey granite. Light grey coloured zinc cappingis used throughout.
Financial viability was only possible by maximising the new building envelope, writes Belsize Architects. It was agreed therefore that the scheme should not only sit as close to the adjacent apartment block as possible, but also include a habitable basement. Building so close to the apartment block presented structural design challenges, and the presence of a shallow railway tunnel only one-metre beneath the site required painstaking negotiation with Network Rail a great deal of work by the structural engineer.
The resulting four-metre deep basement comprises a reinforced concrete box structure with perimeter contiguous piled walls and concrete slabs at basement and ground levels. The basement slab is a piled raft, and as there is the possibility of net heave, tension piles are provided to resist up lift. A waterproof tanking system lines the basement. The building structure comprises a steel frame with precast concrete floors.
The scheme features a number sustainable servicing technologies including high-efficiency gas-fired condensing boilers incorporating variable speed pumps. System controls allow the time and temperature settings within each room to be individually adjusted to minimise heating requirements. Basement ventilation is provided by a supply and extract system incorporating heat exchangers. This enables around 90 per cent of the heat to be recovered from outgoing exhaust air.