Silbury including gate piers and plinth wall

Silbury is an Edwardian Baroque house built in 1906 to designs by Amian Lister Champneys. It now serves as a student residence for Trinity College. The house is constructed of brown brick laid in Flemish bond with red brick dressings, beneath a machine tile roof.

The building is approximately rectangular on plan, facing west onto Grange Road, with a single-storey projection to the north that was formerly used as a boiler room and store room.

The main elevation presents a two-storey structure under a hipped roof with a dormer attic, a modillioned eaves cornice, and two chimneystacks to the east slope. The attic features two bowed dormers to the west slope, each containing five casement windows and hung tiles beneath with a flat roof. Single canted dormers appear on the north and south slopes, and two canted dormers on the east slope; each canted dormer contains six casement windows and a flat roof.

The symmetrical west elevation to Grange Road displays brown brick walls with red brick quoins and surrounds and a red brick platband over the ground floor. The first floor contains 14 window bays arranged in four groups of three, with a central pair of four-over-four pane sash windows at the centre. Each outer group consists of a six-over-nine pane sash window flanked by two-over-two sash windows on either side. The ground floor has three bays of two-over-three pane sash windows to each side of centre. A central segmental hood supported on console brackets with scrolled decorative detailing surmounts a half-glazed door with plain overlight and a six-over-six pane timber sash window. The north single-storey range displays three casement windows to its front elevation.

The garden elevation is symmetrically composed with twelve bays of six-over-nine pane sash windows to the first floor and nine-over-nine pane windows to the ground floor, arranged in pairs either side of two full-height bays. Each bay contains three windows on each floor. The central ground floor openings consist of a half-glazed timber door with plain overlight and a nine-over-nine pane sash window to the south.

A central, flat-roofed, single-storey projection extends from the south elevation's ground floor, detailed with a modillion cornice. Its roof rises in a round arch over a glazed double-leaf door surmounted by a plain overlight and fanlight, flanked by four-over-six pane sash windows. At first floor a six-over-nine pane sash window sits centrally beneath the canted bay in the attic.

The interior preserves the Edwardian Baroque character with classical detailing throughout. Original cornices, skirting boards, and raised and fielded timber doors survive. The half-glazed front door opens into a central entrance hall leading through to the garden door. A round-headed arch from the entrance hall opens into the stair hall, which features parquet flooring and a double-height open-well stair to the first floor. The stair has carved balusters interspersed with simple panel splat balusters and scrolled ornament to the brackets of the open-string and base of the square newel post. South and east doors from the stair hall lead to larger rooms now in use as a professor's study and academic offices. The study's chimney breast includes splayed plasterwork above the picture rail with a stepped and panelled timber surround beneath; the grate is now blocked. Shelved niches sit between the east and west windows. To the left of the entrance hall, a half-glazed door leads to a corridor serving bedrooms to the east, a kitchen to the north, and a service stair to the west.

The first floor rooms to the south and east of the landing overlook the garden. They contain simple cornices and elegant fire surrounds, some comparable in scale to the study fireplace, others smaller and simply tiled (some are now blocked). A half-glazed door from the landing accesses a corridor with bedrooms to the east and north and a service stair to the west lit by the north dormer window. The second floor comprises bedrooms within the dormer spaces, each containing a simple fireplace. The south dormer on the west elevation serves as a small kitchenette for second-floor occupants.

A plinth wall with stone coping stands to the west on Grange Road, featuring two sets of brown brick gate piers with red brick quoins and carved stone capstones.