Numbers 18, 19, 21 and 21a and Attached Railings

A group of terraced houses, now offices, dating from approximately 1810. The buildings are constructed of discoloured brick in a Flemish bond pattern, with stucco dressings and mansard roofs covered in Welsh slate. Numbers 19, 21, and 21A are four storeys high with a basement, while number 18 has no basement. The original two-window range of the houses is present, though the current numbering doesn't reflect this arrangement.

The entrances are round-arched; those facing Northampton Square have engaged Greek Doric columns, a cornice with a Greek key pattern, a fanlight, and panelled doors of original design. The return to Ashby Street has a flat-arched entrance with a simple doorcase and an overlight. The return to Sebastian Street features one entrance with Ionic columns, acanthus leaf decoration to the necking, a modillion cornice, a fanlight with decorative glazing, and a panelled door of original design. A further entrance exists in a single-storey extension to the east, also round-arched with a cornice and fanlight, flanked by coupled pilasters supporting an entablature. Ground-floor windows are round-arched, set within a round arch with a gauged brick head; a stucco storey band separates the floors. First-floor windows are flat-arched, with gauged brick heads recessed within a round-arched panel also with a gauged brick head, and individual iron balconies. Second-floor windows are flat-arched. Original 6/6 sash windows are found in number 21A on the first and second floors. A brick dentil cornice tops the building, followed by a parapet. Dormers are present in the mansard roof, and original stacks project from the party walls.

The return to Ashby Street has flat-arched ground-floor windows and lacks arches above the first-floor windows; 6/6 sash windows of the original design are present in the upper floors. The return to Sebastian Street displays a four-window range, with the two windows closest to Northampton Square being blank, and retains an original rainwater head. Area railings featuring urn standards and spearhead finials are attached to the front.