Exterior
Nantclwyd Hall is a large brickwork house of two storeys and an attic, facing north; its C19 entrance front to the west, and its garden elevation, to the south, remodelled and refronted in render.
The original C17 part projects from the north front. It is in small-size handmade bricks on a limestone plinth, with a hipped slate roof and a large bracketed cornice. It is of three bays width with a single bay return at the right and a three bay return at the left. The window dressings and quoins are in yellow freestone, and there are stone string courses at sill and window cornice heights on both storeys. The windows are cased in stonework with moulded sills, eared architraves, pulvinated friezes and moulded pediments with carved features in the tympana. The latter are of varied character with grotesque touches. The central window pediments of the left flank are curved, the others all triangular. The windows are all of cross type with timber mullions and transoms and quarry glazing.
To the left of the older part, considerably set back, is a six-window C19 range including an advanced bay in the second position from the left and the main door of the house, refashioned in the C20, in the fourth position (i.e. at the centre of a three-bay range). The sixth bay, adjoining the older wing, is set at 45 degrees. This range has a return elevation to the east of three windows, including a two-storey canted-sided bay at left. To the right of the older part, slightly set back, is a later C19 six-window range including an advanced bay in the second position from the right in which is a minor door. This range has a three-bay west return entrance elevation, the centre bay advancing and containing the former main door. There is thus a broad symmetry in the late C19 design, and in detail the C19 architects copied the features of the original wing which remained as the centrepiece, departing only in their use of sash windows in place of cross casements. In the late C20 dormer windows were added throughout the north, east and west sides.
The garden elevation of the Hall, to the south, is the work of Sir Clough Williams-Ellis c1960. This consists of a five-window range to the west and a three window range to the east, in which the roof, plinth and quoins details of the north side are repeated, but the walls are finished in plain colour-washed render and the windows are in un-ornamented openings. Between these unequal ranges, and itself asymmetrically placed, is the centrepiece gabled unit, with link-ranges to left and right. This centre-block has a Dutch gable with a coped upper part to its parapet and side urns; a decorative roundel on the gable; two small attic windows; a venetian window with stone casings; a decorative swag with the initials E A F-H and V E N-L and the date 1959; and three round-headed ground-storey voids, the centre for a sculpture, the outer ones French windows.