'It required ingenuity to unlock the potential and open up the cellular structure of this house, ' explains Neil Choudhury.Although it has a posh NW3 postcode, the house in question is in a surprisingly modest terrace, Gayton Road, and the rooms were generally small and dark. It had been bought by a young family, previous clients of Choudhury.
The house was on three storeys, but the rooms were cut off from the garden by the basement, a separate flat with its own front door to the street. Since the floors were connected by a typical single stair arrangement, regulations did not allow this to be continued down to basement level.
Choudhury's ingenious solution was to open up the spaces at basement and raised ground floor level and connect them by means of a new staircase set in a glass extension at the back of the house. The extension replaces a dark and uninviting basement courtyard and slots in between the original three-storey back extensions. The roof, external wall and upper floor platform are all made of glass. The result is a transformation. 'Now the whole house is flooded with light, ' says Choudhury. 'And it has a new, almost poetic relationship with nature, not only the garden - where the new view focuses on a significant mature tree - but also the changing skies, and the rain on the glass roof.' The etched glass floor diffuses light to the lower ground floor while reflecting daylight into adjoining spaces. The large area of glass was possible because it faces north-west and is protected by the surrounding three-storey walls.
The new stair is steel with solid maple treads to give a sense of security - and for economic reasons. It rises in a straight flight from the basement and is screened from the adjacent glass platform by a solid maple balustrade - again to give a sense of security.
The glass platform is designed as an extended part of the kitchen - the fitted kitchen table extends into it and there is room for seating where the family can eat and look out through the glass wall.
The glass extension is modest in appearance- in fact it is hardly noticeable from the rear garden and neighbouring gardens. (The architect was required by the local planning authority to minimize its impact. ) Choudhury says: 'We considered the use of a glass supporting structure but rejected it because of its fashionable connotations. Instead we took a more direct approach - 130mm deep steel flats for the principal roof and wall structure, which were fixed directly to the walls of the existing rear extensions and could be restrained with countersunk bolt fixings.'
The glass roof slopes imperceptibly from the eaves to a concealed gutter at the junction with the existing house. This allows a simple eaves flashing under the glass roof panels that is only 130mm deep. The glass roof panels are as large as possible within the limits of what could be passed through the house and existing rear window openings.
With four double-glazed panels only three visible cross-supports are required.
The glass floor platform is supported on a 150 x 90mm steel channel facing outward to reduce its apparent size. This is supported at the existing walls and at the corner on 60mm circular hollow section column. The space is relatively small and all steel members are kept to their minimum size. Connections are either welded or bolted. 'We used the simplest possible fixing system since in such a small space you are always very close to the connections and we felt that detailing would soon become tiring, ' explains Choudhury.
The budget for the extension was modest.
It cost £26,000 - excluding garden works.
Ifyou want to work for Neil Choudhury Architects turn to page 46.
ARCHITECT Neil Choudhury Architects: Neil Choudhury, Henk Weiringa STRUCTURAL ENGINEER Ellis and Moore: Harry Mourdjis CONTRACTOR Dave Goodman SUPPLIERS glazed roof Cantifix; steel doors and windows Metal Window Service Company; laminated glass floor Glaverbell; radiators Radiating Style