Bureau de Change uses heritage-inspired precast details to reimagine a 1930s London house
Architect Bureau de Change has married traditional brickwork with exposed in-situ concrete and intricate precast details to offer a modern interpretation of the 1930s gabled houses of Clapham, south London.
Fitting within the height and footprint of the previous 1930s property, the 420m2 four-storey Cast House is formed from in-situ concrete on the basement and ground floor and red brickwork above. The architects have incorporated traditional motifs into the cast concrete, including bay windows and corner details that invert the brickwork pattern above. The traditional front porch has been reinterpreted as a pared-back concrete void with a recessed seat cast in. The formwork was faced with medium-density overlay boards to leave a matte finish to the exposed surfaces.
The concrete work also includes a number of more elaborate details, such as framed lintels and slender transoms and mullions, which have been precast on site and mechanically fixed to the structure. Bureau de Change worked with architectural concrete consultant David Bennett Associates on the formwork design, experimenting with different proportions and finishes. A 100% Portland cement mix was needed to provide the necessary strength, with softwood inserts used to create the mouldings.
At the back of the house, the living accommodation is arranged in three stacked concrete boxes. The largest of these volumes, which cantilevers over a basement patio, houses the living, dining and kitchen spaces. Above this, smaller volumes contain bedrooms, with the top unit projecting from the roof like an outsized dormer window. Each of the boxes has a full-height window overlooking the garden, while the stepped arrangement creates private terraces at each level. A stonelike texture has been created on the sills and the steps leading down to the sunken patio by grinding the concrete surface to uncover the aggregate.
The exposed concrete was bag-washed with white cement to fill all bolt holes and fixings and to leave a consistent, stony white finish in contrast to the surrounding red brickwork.