Design Awards: 2005: Certificate of Merit

Private House, Kingstown St, London NW1

Private House, Kingstown St, London NW1

Architect

Springett Mackay Architecture

Structural Engineer

Techniker Ltd

Steelwork Contractor

Brent Fabrications Ltd

Main Contractor

Harris Calnan Construction Co Ltd

The new house completes a narrow mews in Primrose Hill, North London. Construction on the confined site was complicated by the continuous building frontage and absence of working area around the building. The design of the house makes full use of the available space. A steel framed structural solution was adopted to speed up and simplify the construction process and to allow for the development of ‘lateral space’.

The building is entered from the back of a car parking area sheltered by the first floor overhang. The front door opens into a double height hall with wide steel stair leading up to the main living spaces at first floor level. The stair is carefully detailed with stainless steel handrails and clamp plates to the toughened glass balustrading.

The main structure comprises two storeys of posts and beams set on a foundation of bored concrete piles. The building is approximately 12 metres square on plan and six metres tall. Ground beams and a suspended ground slab support a lower storey of brickwork and lightweight partitions. Subsoil conditions were found to be very sensitive to moisture changes and the pile foundation is taken deep down to the firmer layers of London Clay. Compressible void formers isolate the entire building from the surrounding ground.

The first floor is open plan, column free, with a large window across the entire north elevation. This floor cantilevers out over the rooms below. The wide spans are in-filled with timber stressed skin construction to reduce the overall weight of the building. The floor, wall and roof thicknesses are minimized by the use of universal column sections. Beams and columns are combined to form continuous rings around the upper storey. Axial and bending stresses are allowed to develop in all the structural components so as to reduce overall deflections.

The steel frame was prefabricated and assembled at works then cut into transportable components. Site joints were located away from areas of complicated fabrication and towards points of minimal stress, which could be readily accessed for reassembly. The long cantilevers at first floor level required complicated pre-cambering.
The construction period was slightly less than a year and the frame was erected within the space of four weeks. The dynamic behaviour of the structure was closely studied using a computer model to simulate footfalls. Precise points within the building to be used for study and relaxation were examined to ensure that structural movements would be imperceptible. Completion was in November 2003.

Judges’ Comment

s:

This cleverly planned London pied-à-terre makes the most of a constrained mews site, and improves the local amenity. The living space is in a clearly expressed “box” on the first floor, thus giving advantages of sunny, elegant living rooms with good views to mews and garden.

Steel framing behind the scenes enables these objectives to be achieved beautifully, relying also on a clear working relationship between architecture, engineering and construction.