Plas Newydd

Plas Newydd is a substantial house aligned north-south, with main living rooms facing east over the Menai Strait. The principal structure comprises three storeys built over a double basement, constructed in limestone ashlar masonry with plinth, moulded first-floor sill band and moulded cornice below a plain parapet (formerly with battlements).

The east front displays a symmetrical main block with a three-bay advanced central section featuring a semi-circular bay flanked by windows, stressed by angle pilasters surmounted by Tudor caps. Single windows with four-centred arched doorways separate this from full-height canted bays either side, with a further nine-window range to the right. The windows are 1930s recessed 24-pane sashes to the ground floor, 24-pane casements to the first floor, and 20-pane fixed-light casements to the second floor, all with voussoir lintels and moulded hood bands. A three-storey, nine-window northern continuation in squared rough-faced limestone (replacing an early nineteenth-century chapel with three Gothick windows) extends from this range, with plinth, plain sill band at first floor level and slate roof. Domestic buildings at the north end rise to two storeys, the lower of rubble and upper of squared limestone, retaining original horned sash windows—12-pane to the first floor and 16-pane to the second.

The south return front displays an asymmetrical design with a three-window range and canted bay to the right, the latter being the original octagonal tower.

The west entrance front, built 1797–9 by Wyatt and Potter extending the original hall house, was originally designed as a symmetrical composition with two entrance porches flanking a Gothick-windowed hall, with three-window flanking wings. In the 1930s, symmetry was disrupted when a three-window range was added to the north, linking the main block with a five-window service wing. The limestone ashlar masonry has plinth, moulded cornice below plain parapet (formerly with battlements). The central, slightly advanced two-storey, three-window hall, known as the Music Room, features three tall Gothick windows breaking the first-floor sill band. Similar traceried windows with moulded arched hood band and sill band light the elevated first floor. Flanking octagonal buttress piers with Tudor caps project at the angles of return and either end of the main block. To the south, a three-window range has two windows blocked on each floor, with a Gothick porch of four-centred arch and battlements; the balancing porch in the block north of the Music Room was removed in the 1930s. A two-window range north of the Music Room contains a wide square-headed entrance on its south side with mouldings and Gothick detailing, with narrow arched windows to the north. A moulded first-floor sill band and cornice runs along this section. A three-window range north of the main block links it to the five-window range at the extreme north, which formed the service areas, partly built on the site of the original stables. An ice house and apple store occupy the yard to the west. A screen wall designed by Rex Whistler in the 1930s, featuring voussoir arches with projecting keystones at either end, runs at right angles from the north side of the hall.

The plan comprises two parallel ranges of rooms in filade, divided by a spinal corridor. The easternmost range represents the earlier eighteenth-century house, while the western range largely dates from Wyatt and Potter's work in the 1790s. This western range is broadly symmetrical in layout, with the Music Room flanked by the stair hall to the left and the Gothick hall to the right. The main entrance hall rises through two storeys with a gallery at one end and a fine plaster fan-vaulted ceiling. The Music Room also features a plaster fan-vaulted ceiling and an ornate carved chimney breast flanked by plaster figures of Medieval knights. The north entrance led into the Neo-classical stair hall and anteroom, accessed via a cantilevered staircase with wrought-iron balustrade leading to a landing with fluted and marble-painted Doric columns. The east wing interiors remain substantially as remodelled by Wyatt around 1795, though resulting from earlier phases in plan. Decorative schemes here and in the first-floor rooms are largely the work of Sybil Colefax in the 1930s. The north wing was entirely remodelled 1935–6; its principal feature is now the Rex Whistler Room, containing the artist's last and largest mural, completed by 1940. The mural is a Georgian landscape fantasy based on views from Plas Newydd over the Menai Strait and Snowdonia, interwoven with classical architecture and personal recollections.