Plas Llwynonn including coach house and service range to rear.

Large Neo-Tudor style gentry house of 2-storeys with attic. Built of granite rubble with limestone dressings; roof covering of ornamental 'fishscale' slates with sawtooth ridge tiles, stone copings, kneelers and finials; rectangular stone stacks. To rear is single storey wing with attic, continued as lofted coach house and tackroom. Stables and gate lodge built parallel to house across yard; with stone archway and wall completing yard. Single storey wings to rear of house now form entrances to individual dwellings within main block, linked by lean-to extensions.

Main L-plan block of two storeys with attics, with entrance elevation in right (east) gable return; advanced gabled bay of 2-storeys with attic to left of centre, containing entrance porch with pointed chamfered arch. First floor with 4-light chamfered mullioned window, attic floor with lancet. Left of the porch is the projecting offset chimney breast serving the gable stack above. Right of the porch is a ground floor cross window and 1st floor 2-light mullioned window; to right end is 2-storey bay window with 4-light chamfered transomed and mullioned windows, above which is a raking dormer window of 3-lights. Central stone stack.

Principal elevation, facing S, of 3 gables; paired gables to left slightly advanced, each with 2-storey bay windows, with 3-light chamfered transomed and mullioned windows, with hood bands and sill strings, surmounted by parapets with ball finials. Between the twin gables, ground floor 3-light transomed and mullioned window with hood mould; 2-light window to 1st floor; attic storey has 3-light mullioned windows with hood moulds. Similar fenestration to recessed right-hand gable. Three rectangular stacks, 1 to each end and 1 to right of advanced bays.

To left of main block is a 2-storey L-plan range, formerly servant's quarters, of similar materials, including 2-storey with attic gabled bay to left. 3-light chamfered mullioned window to ground and first floors, that to ground floor with continuous hood string; attic floor with blind slit window. Two-window range linking main block to right has 2-light chamfered mullioned windows, door to right. Lofted domestic range and coach house to rear with 3 brick cambered arches to right, with slate-roofed verandah supported on tapering columns; tackroom to right end; single storey with embattled parapet, through passage with pointed arched openings and single 16-pane sash to right. Set at right angles to rear of main house, and to domestic wing, are 5 single storey wings with a mixture of pointed and elliptical arches to doorheads, with plain hoodmoulds.