Coupar House, at the corner of Church Lane and The Plocks, is probably of c. 1750; in 1731 the site was an open garden with a small building at the middle of the West side  the West range has a normal Group (i) plan and is of three storeys. The East range is differently orientated from the West and therefore appears to be of another period; presumably it is earlier since the top floor of the West range is accessible only from the East range.

Coupar House is the largest and most splendidly decorated private house of the post-fire period in Blandford Forum, and the only one to have the richness of Portland stone dressings on its brick façade .In the front garden, handsomely carved urn finials surmount the piers which flank the gateways and occur at intervals in the wall. Despite the use of costly materials the façade is curiously amateurish in design. The various elements of the composition, adequate in themselves, are ill co-ordinated and little attention is paid to rules of proportion. The interior is richly fitted and the main staircase is the handsomest in Blandford.

The brickwork of the West front consists only of headers, red bricks being used in the wings and blue bricks in the central feature. In the two lower storeys the central feature is flanked by Ionic pilasters carrying an entablature with a pulvinated frieze just above the first-floor window heads. The lower orders of the entablature distinguish the central feature alone but the cornice continues across the whole façade, terminating at French quoins at the extremities of the five-bay elevation. Above the cornice the second storey has at each extremity a panelled stone pilaster superimposed on the quoin below, and French quoins on each side of the centre bay superimposed on the Ionic pilasters. The façade is capped by a second cornice, returned as a pediment over the central bay. On the ground floor the central doorway is flanked by three-quarter columns carrying a full Doric entablature and pediment. Above, the middle first-floor window has an eared architrave, scrolled stone cheek pieces and shaped consoles to the window-sill. The lintel and keystone are squeezed with difficulty into the space below the main entablature, the window architrave being thinner than it should be and the keystone cutting into the fascia of the architrave; this is a serious fault of design, and strange in view of the fact that the same problem had been successfully evaded   The round-headed middle window of the top storey is extended by false panes into the field of the pediment and surrounded by a rusticated architrave with a triple keystone. The lateral windows are simpler than those of the central feature; they have stone architraves with plain keystones, and on the first floor they have sills with shaped consoles.

The stonework of the west front does not extend in the North and South elevations beyond the returns of the corner members. On the South side, both cornices continue across the end wall of the main range in brickwork and follow the projection of the South chimney-stack. On the North wall of the range, the main cornice is not represented and only the upper cornice continues at the foot of the gable. There are no windows in either end wall.

Inside, the square vestibule has a dado of fielded panelling capped with a moulded rail which turns up to follow the stairs and is continued on the first-floor landing. On the ground floor, doorways to North and South have eared architraves and sixpanel doors; the entrance doorway is similarly treated but with an eight-panel door. The carved oak stairs have an open string and a rich version of the Tuscan-column balustrade that is usual in 18th-century Blandford buildings; each tread carries three balusters and the moulded handrail ends at the bottom in a fist-shaped scroll. The square end of each step is panelled and the spandrel below the panel is enriched with a foliate scroll. The South west room is panelled to its full height with fielded 18th-century panelling, the middle panel of each wall being accentuated by bolection mouldings; the dentil cornice is of wood. The marble fireplace surround is flanked by foliate scrolled cheek-pieces; above rests a pulvinated laurel and acanthus frieze with an oblong centre panel on which is carved a delicate swag of flowers and fruit; the overmantel has a shouldered centre panel flanked by fluted composite pilasters supporting an entablature with a broken pediment. The North west room  is decorated in much the same way, but with a cornice enriched with egg-and-dart mouldings, a tier of fluted modillions alternating with rosettes, and a fillet of leaf-and-dart below the plain corona. The door heads have flat entablatures with pulvinated leaf friezes. On each side of the fireplace is a round-headed recess. The fireplace surround is flanked by pilasters with pendant leaf festoons crowned by scrolls with scale decoration on the front; these are spanned by an architrave with wave ornament, above which a foliate scroll extends on each side of a central panel; the overmantel consists of an eared architrave with guilloche enrichment flanked by foliate scroll cheek-pieces and crowned by a pediment.

On the first floor the stair hall has a moulded plaster ceiling. The South west room has wall panelling of much the same style as in the room beneath, but less rich. The 19th-century fireplace has a reeded stone surround with roundels at the corners; over it rises an overmantel composed of large acanthus brackets supporting a broken pediment and flanking a flat panel with foliate cheek-pieces and a scrolled head. The North west first-floor chamber has no panelling; its cornice resembles that of the South west room on the ground floor.

The passage between the East and West ranges is lined with wooden panelling from the North end to a transverse arch about half way along it. The North east room is wholly lined with fielded panelling above and below a moulded dado rail. The adjacent room has a plain dado rail of c. 1820. Towards the South end of the passage, stairs lead up to the first floor of the West block, which is also entered from the half-landing of the main staircase. The first-floor North east room has a bolection-moulded overmantel and a moulded wooden cornice around part of the ceiling.

The house is separated from the street by a forecourt 30 ft. wide, bounded by high brick walls which terminate at stone piers on either side of an iron-railed centre section. The piers have panelled sides and moulded cappings and support carved stone vases. Other vases decorate brick piers at the North and South ends of the court.