Design Awards: 2015: Certificate of Merit

Kew House, Richmond

Kew House 1

Architect
Piercy&Company

Structural Engineer
Price & Myers

Steelwork Contractor
Commercial Systems International

Main Contractor
Tim & Jo Lucas

Client
Tim & Jo Lucas

Set within the Kew Green conservation area of south-west London, this four bedroom family house is formed of two prefabricated weathering steel volumes inserted behind a retained 19th Century stable wall.

The site lies directly on the street and is oblong in plan, 18m wide and 10m deep. This small size and the surrounding brick walls between it and neighbouring gardens were key constraints in the development of the structural strategy for the house.

A key feature of the building is the weathering steel façades and roof. The house is split into two gabled forms which are joined by a glass link that houses the circulation – steel stairs, a link bridge between the two sides and a plywood slide down into the basement.

The roofs are made as structural stressed skin shells in 4mm weathering steel, strengthened with internal mild steel stiffeners. The roof shells form the watertight enclosure to the building, like an upturned hull of a boat. The shells have an intricate array of details, including perforations, expressed welded joints and concealed gutters and drainage channels around window openings, that retain their clean lines whilst making the shells functional as a building.

The shells were fabricated in 10 large modules offsite and shot blasted before being brought to site and lifted in using a lorry mounted crane. This approach allowed both the structure and roof finishes to be constructed from within the site boundary. The modules were site welded together to waterproof the joints before being lined with insulation, fitted with windows and drylining to give a total wall thickness of only 200mm.

The steel staircase forms a principal feature of the house in the glazed link. It is very slender, with a well thought out arrangement of stiffeners to give it the required strength to span 6.5m between the two sides of the house. After installation it was decided to leave it exposed rather than being covered in timber.

The engineer client took part in the building process by fully modelling the weathering steel shells in 3D, structurally designing them to an intense level of detail to include recessed built-in gutters, thermal breaks and windows flush with the outer face.

The prefabricated nature of the complex weathering steel shell meant that design challenges could be solved in the studio with architect and engineer collaborating on inventive and cost-efficient solutions.

Judges’ comment

Through its use of weathering steel as the primary structural and visual material, and the ingenious use of the site, this private house can claim to enhance the conservation area. The prefabrication of the roof shells, a technique more familiar on large projects, is a powerful illustration of the potential of steelwork in domestic building.

This project merits attention for the potential of steelwork in domestic architecture.

Weathering Steel House, Putney

Weathering Steel House Putney 1

Architect
Eldridge London

Structural Engineer
Elliott Wood

Steelwork Contractor
Suffolk Welding

Main Contractor
Famella

This project involved redevelopment of a garage building in south west London into a high-spec private house set out over four floors including a single basement. The rust- like appearance of the weathering steel cladding is a striking feature of the cutting- edge design of this private dwelling.

The house is in two distinct parts. At the front is the main four storey building, clad in weathering steel sheets interspersed with large glazed areas. At the rear is a separate single storey living space complete with glazed elevations and a green roof. The two areas are joined at ground floor level by a transparent corridor complete with a glazed roof, walls and floor sections; below ground the areas are also linked by a concrete basement which runs to the edge of the single storey living space.

The concept for the superstructure of the house was for it to be a monocoque, whereby the façade system also acted as the primary structure to the building. The finished material therefore needed to be sufficiently stiff to act structurally, as well as provide a weathertight enclosure and architectural interest. In addition to the architectural requirements, the constructional issues were significant. The footprint of the proposed house stretches between the boundary lines, leaving little working space for the contractor when onsite and required careful planning to construct a significantly challenging structure.

Steelwork was adopted as the primary structural material, with weathering steel as the external finish. This met the architectural requirements set out, as well as allowing the use of cladding as a stressed skin in combination with ribs, minimising requirements for additional primary structure to the perimeter. The use of a monocoque type structure was developed towards a series of prefabricated pods that could be erected onsite quickly and accurately. Connections were achieved by simply bolting the pods together onsite and then welding the weathering steel at its ‘seams’ to form a weatherproof envelope. To minimise heat loss, the connections between the panel and the internal floor structures were carefully detailed to prevent the junction creating a thermal bridge.

The prefabricated boxes were initially trial erected in the steelwork contractor’s workshop, which gave the opportunity to begin structural glass procurement far earlier in the programme than would usually be possible. This greatly improved speed of construction of the structural elements.

Judges’ comment

A house for a private client with individual demands, this elevates the use of structural weathering steel in domestic architecture to the level of bespoke tailoring. It illustrates what can be achieved by the closest attention to detail, and unified teamwork by architect, engineer and steelwork contractor/erector, as all details have been considered, coordinated and beautifully made.

Congratulations to the team for a meritorious labour of love.