Upper Lawn Cottage (Solar Pavilion), with associated garden walls and raised patio

Upper Lawn Cottage, known as the Solar Pavilion, is a small domestic building designed and built in 1961-62 by Alison and Peter Smithson as a holiday home for themselves. It stands in West Tisbury near Upper Lawn, incorporated into an eighteenth-century walled garden.

The building is constructed using the remains of an earlier eighteenth-century stone cottage as its structural base. Above this foundation sits a timber American balloon-frame structure supported by concrete beams. The exterior is clad in teak and aluminium where not glazed. It has a rectangular plan with two rooms separated by the fireplace of the original cottage.

The house is arranged as a two-storey building with a piano nobile (principal living floor) above service rooms. Three elevations face south onto a courtyard and are composed as Miesian walls of glass. The courtyard-facing elevations on the ground floor are framed in teak with retractable glazing that opens fully into the courtyard. An aluminium cill band separates the two storeys, and an aluminium cornice tops the flat-roofed building. The north-facing elevation, constructed from uncoursed ashlar, is the rebuilt and fenestrated wall of the walled garden on the ground floor. Glazing wraps around the eastern bay at first-floor level, while the west elevation is clad in aluminium.

The interior is lined throughout with cedar plywood. The ground floor contains a kitchen with modern fittings from 1970 in the western bay, a sink and shower room to its rear, and a garden-room in the eastern bay with built-in window seat and bench seating. The ground floor has sealed concrete floors; the first floor, accessed by a fixed timber ladder stair, has boarded timber floors.

The eighteenth-century rough stone garden walls extend either side of the house and enclose the garden. These walls incorporate the remains of eighteenth-century cottages demolished for the pavilion, including windows (all but one blocked) and a far chimney stack. The footings of the original cottages form a raised terrace.

Alison and Peter Smithson, who met at Durham University and married in 1949, had established their architectural partnership in 1950 after working for the London County Council. Their practice became closely associated with the New Brutalism movement, which they essentially founded. When they acquired Upper Lawn in 1958, the site comprised a half-derelict thatched cottage, probably originally a pair of cottages, built into the north side of the walled garden. Initial designs by Alison date from 1958-59, and a detailed photographic record by Peter documents construction in 1961-62. The original eighteenth-century structure had a three-room plan with fireplaces at each end and an unheated room in the centre. The eastern bay had collapsed by 1958. The Smithsons retained the garden-enclosing walls and the fireplace walls at either end; one fireplace wall became the central cross-wall of the new house, with one bay to the east on the site of the original house and a second bay extending westward to house the main living room, kitchen, and bathroom added from 1970. This configuration was adopted to capture views toward Fonthill Abbey to the north and west, which was landscaped by William Beckford in the early nineteenth century.

The building carefully expresses the Smithsons' Brutalist manifesto, published in Architectural Design in January 1955. It was restored in 2002-03 by Sergison Bates, with engineering by Derek Sugden of Ove Arup and Partners, later Arup Associates.

This is the only building designed, built, and inhabited by the Smithsons for their own use and one of their few realised domestic projects.