The project is for the construction of a new 800 m2 house on an enclosed back-land site in Notting Hill, London, for a family of two academics and their two children. The clients had previously lived in typical London vertical town houses of up to five stories, and wanted the house to be connected and interactive by being more horizontal. The brief required a very private house for the family to live and work in, a suite of living rooms, a kitchen, two studies, a library, dining room, chapel, five bedrooms and bathrooms, a swimming pool, courtyard gardens, garage, wine cellar, laundry rooms and plant rooms.
We worked for over a year with the client to find the plot of land which with the restrictive planning laws in the UK would allow a contemporary structure to be built. We had experience of working with back-land sites (essentially redundant factories or warehouses in residential areas) in London, and concentrated on these in our search. The site we eventually found was ideal as the planners would only allow a single house on the site and was very well located in an area well known to the clients. However as is typical of back land sites, there were problems of access, overlooking and overshadowing to overcome, as well as a requirement for fourteen different party awards with neighbouring owners.
The empty site was essentially a box 40 m deep by 15m wide 10 m high on one side and up to 8 metres high on the other sides, consisting of brick party walls. We were not able to apply any pressure to the party walls having to build an entirely independent structure, and had a requirement for very large planes of walls extending up to the top of the 10m high wall.
In situ exposed concrete was a natural choice- it acts as an environmental moderator (the house is naturally ventilated), the exposed finishes put workmanship on display, and structurally there was a requirement for large vertical cantilevers and beams. A grillage of deep tapering beams span from vertical cantilevers 8m-10m high and 32m long, forming the high level enclosure to the room below. These ‘rooms’ range in size from 18m x 3m at the largest to 3m x 3m at the smallest.
The complexity of achieving this apparent simplicity was deceptive. 14 separate party wall awards were required and the site is only accessible through an arch 3m wide and 4m high. The vertical cantilevers needed to be built within 150mm of the existing walls, and no pressure could be placed on the party walls during construction. Our subcontractor developed a method utilising specially designed and fabricated steel shuttering at the back of the wall taking the forces through to the front of the shuttering, which was propped back onto the slab. Due to the restricted nature of the site, the project had to be built from the back of the site in stages towards the front of the site, as mobile crainage was the only solution possible for placement of concrete and movement of shuttering.
Careful research on the concrete specification was carried out by ourselves, Arup and the client- whilst concrete was an early decision, there were concerns relating to achieving the finish and colour required. Site visits from London to Berlin were undertaken in order to narrow down what was wanted, and possibly more importantly, what was not wanted. We were looking for an ‘as struck finish’ with no making good. Some character was also a requirement, rather than a very flat even colour throughout. These are issues that are subjective and therefore difficult to include in a specification. The solution was to research the methods used in the concrete we did like, and write the specification from that point. Trial panels were specified, and the basement walls used to test various chamfer and bolt hole details, as the evenness of the bolt holes both in finish and setting out were very important.
The house in naturally ventilated, which is controlled by means of thermal mass, shading, and air movement. The roof, although made of 300m2 of glass, has a highly effective solar coating, three different frit densities to the glass, electrically operated blinds, and opening vents, all of which contribute to a high level of control of the internal environment by the occupants.
A very restricted palette of materials was used throughout the house, consisting of stainless steel, concrete, glass and aluminium. Polished concrete screed floors, stainless steel lined swimming pool and bathrooms, exposed concrete structure to the walls and beams, stainless steel kitchen, aluminium framed sliding doors and windows, perforated corrugated stainless steel used as cladding and external screens and doors.