Plas Llangattwg

Plas Llangattwg is a Georgian country house with fine symmetrical front showing Regency improvements. The main block is three storeys and three bays under a hipped roof, with a central pediment and rusticated quoins to the main elevation. Flanking this are two-storey side wings with parapets concealing lean-to roofs. A staircase turret projects to the rear, along with further ranges. The roofs are slate with rendered end stacks, and the elevations are painted roughcast.

The front elevation features a moulded dentilled eaves cornice. The central pediment contains a similar cornice and an oculus with radial glazing. A fine decorative wrought iron veranda of two storeys fronts the house. It is supported on eight posts composed of narrow strands of iron, with an iron latticework screen against the wall, presumably for climbing plants. The first floor supports a cast iron porch canopy with swept roof and finial. The central front entrance has an ornate gabled doorcase with fluted pilasters, capitals and bases and a moulded cornice. It contains a round-headed doorway with half-lit panelled double doors and fanlight. The entrance is flanked by square-headed French doors, each of three panes with further rows of glazing above and to the sides. The first floor has three pairs of French doors, the central pair narrower and under the iron canopy, with flanking French doors like those on the ground floor but without the upper row of glazing. The upper storey has nine-pane hornless sashes—a single central window flanked by paired windows. The side wings are single-window with twelve-pane sashes to each storey and stone sills.

The west wing continues southwards as a long two-storey range. Its west side has irregularly placed sash windows: four twelve-pane sashes to the upper storey and a small six-pane window, with two twenty-pane sash windows towards the centre of the ground floor flanked by twelve-pane sashes. A brick stack rises to the rear of this range.

The east wing is two-window with a sixteen-pane horned sash at the north end and a sixteenth to seventeenth-century window at the south end—a three-light casement with timber hexagonal mullions and quarry glazing. The upper storey has two twelve-pane sashes. At the south end of the east wing is a porch with panelled door leading into a rear lean-to, now disused. The square porch has an entablature supported on four columns. Extending southwards from the door is a random rubble garden wall with a basket-arched entrance into the rear garden.

The rear is dominated by a full-height gabled stair projection with twelve-pane sashes at landing height to the first and attic storeys, flanked by two gabled roof dormers containing multi-pane casement windows. In the lower storey, a door leads into a flat-roofed extension. Lean-tos flank the staircase projection. That to the east incorporates part of the Tudor house and has two sixteen-pane sashes to the upper storey and a large five-light multi-pane window below. The lean-to on the west side of the projection is slate-hung with a small four-pane window but is mainly concealed by the flat-roofed L-shaped extension. At the south end of the flat-roofed extension, abutting the west wing (which has a twelve-pane sash to the rear), is a square range with hipped roof. From this extends a masonry boundary wall.

The south end of the west wing abuts a further long range on the same orientation which may be earlier. This is a range of service buildings which included stables, a cart shed and possible groom's accommodation, with a hay loft over. It is masonry under slate roof with a large masonry ridge stack. The south end now contains a garage with wood-planked doors and two further twentieth-century doors. There is also a four-pane window and a nine-pane window. The former hay loft has a raked dormer with wooden shutters. The west wall faces a public footpath and shows evidence of infilling between masonry piers. There are a few small wood-framed windows but otherwise no features.

The house is entered from front and rear into a large central stair hall. The full-height dog-leg staircase is on the right (west) side and extends into the rear projection. It is of oak with a swept handrail, three balusters per tread and a substantial round-section newel post. The hall has oak floorboards. The dining room is to the right and the living room to the left of the hall. In the living room, the French doors are below a decorative metal pelmet. There are two large arched recesses in the living room, with moulded coving, panelled shutters and doors throughout. From the rear entrance, Tudor-arched openings lead into the stair hall and into the lean-to room behind (south of) the living room. This lean-to room contains Tudor features: a boxed-in cross beam, the timber-mullioned window, and part of a curved stone staircase. The interior of the long service range to the south of the west wing contains evidence for fireplaces and beams.