6th June 1996

A Hampstead house and garden linked by glass

A garden pavilion by The Architects Practice illustrates how glass can be a fine structural material while lifting the spirit
By Marcus Field.

The exercise pavilion, conceived as a garden room, nestles in a corner of the site. It consists of a steel frame, raised on piles with a frameless glazed roof over the main exercise space.

Beyond the northern reaches of Hampstead Heath the Victorian streets give way to broader avenues lined with some of the most expensive and ostentatious houses in London. Tucked away in one of these roads is a house which has recently been remodelled by The Architects Practice and had its garden landscaped.

With the exception of a contemporary-looking balcony and a bar made almost entirely of glass, the works to the house are fairly conservative. But beyond this, nestling among mature oak trees at the rear of the garden, the architect has placed an exercise pavilion which defies its surroundings in its crisp detailing and structural innovation.

Conceived as a discrete garden room, the building is designed to link the house, the newly built pool and landscape in terms of composition and materials. Structurally the building consists principally of a steel frame raised up on piles. A flat, frameless glazed roof sails over the main exercise space, its transparency maintained by the use of laminated glass beams and columns as structure.

A steel lintel over the front doors also rests on glass columns. Shaded by the surrounding trees in summer and serviced by underfloor heating in winter, the achievement of this transparent space is to offer a year-round building for exercise which is as open to the outside as possible. From the gym machines which now fill it, there are views to the house, garden, pool and beyond to the undulating golf course.

On either side of the exercise room, two steel-framed wings infilled with timber-clad insulated panels accommodate changing and sauna facilities, a marble-clad vaulted steam room (a serene space like the inside of an elegant tomb) and a plant room.

Beyond these and screened from the gym is a secluded kitchen and bar which give out on to a private terrace and spa.

Simon Foxell of The Architects Practice sees a strong relationship between his pavilion and the architecture of oriental exampIes , quoting a passage from Chinese Pavilion Architecture by Werner Blaser as his reference: 'The principle of skin-and-skeleton requires the structural members to be minimal and the enclosed space variable, thus allowing rooms to merge one into the other and surrounding nature to form part of the spatial experience. A simple construction of columns ensures that freedom in the interior which is a pervasive feature of Chinese pavilion structure. At the same time it establishes the relationship with the landscape.'

Given the technology of the structural glass in Foxell's pavilion, it comes as no surprise to find that the engineer is Tim Macfarlane of Dewhurst Macfarlane, the same firm responsible for the structural achievement of Rick Mather's much published conservatory in nearby Hampstead. Together the modest-sized projects illustrate the potential of glass as a contemporary construction material and as a means of creating a building which is not only functional, but also uplifting to the spirit."

Working details
By Susan Dawson

The single-storey pavilion stands among trees at the apex of a triangular garden plot, and its wedge-like shape follows the boundaries. It is a steel-framed structure of paired 152 x 76mm channels set back to back 75mm apart, raised off the ground on 15 bored, cast in-situ piles.

It consists of a wedge-shaped gym with a fully glazed east wall and a glass roof, flanked on each side by two wings clad in oak boarding and roofed in stain-less-steel sheet. At the west end of the building is a fireplace with a freestanding external chimney.

The glass roof and the glass wall are of frameless glass sheets supported by laminated glass beams and glass columns, a concept first developed by Rick Mather and Dewhurst Macfarlane (AJ 22.7.92). Seven 225mm deep glass beams support the glass roof; the four outer beams rest on the steel structure; the three inner beams span from an 850mm deep triple-laminated transverse glass beam towards the rear of the building, to 3.4m high laminated columns along the glass wall.

The beams and columns are made of three sheets of l2mm glass laminated together with a 1mm interlayer. They are connected to the columns by cutting and splicing the laminated sheets to form unbonded mor-tice and tenon joints, secured by the structural silicone joint between roof and wall sheets.

The roof is of double-glazed units which are precisely cut so that the two edges of adjacent panels abut on to the 36mm thick glass beam. The glass wall is fitted with a pair of 10mm tough-ened glass doors with transom panels above them, supported by a steel lintel, a 152 x 152mm UB with an extended top flange. The glass columns on each side sup-port the lintel; they are laminated with an additional 12mm-thick layer of glass which gives bearing to the lintel edges.