Royal Intitute of British Architects Drawings Collection

The Royal Institute of British Architects Drawings Collection is an end-of-terrace town house built around 1772 by James Adam for the collector William Loch of Norbury. It features fine Adam interiors and is constructed of brown brick with a concealed slate roof. The building's elevation is designed to form a cohesive composition with No. 20 (Home House). It stands four storeys tall, including an attic storey added later, and has a basement. The façade is three windows wide, with a five-window return that includes an entrance to Gloucester Place, featuring a canted bay to the north.

The semicircular arched doorway, with sidelights and a fanlight, is situated under a stucco Doric porch on the return. The ground floor has sashes set in a blind arcade that continues from No. 20, with similar stucco roundels in the spandrels. The first floor features French casements facing Portman Square and glazing bar sashes on the upper floors, all under flat gauged arches. Decorative elements include guilloche bands, garlands, paterae panels, and a cornice that matches No. 20. The attic storey has a crowning cornice but lacks a balustraded parapet. There is a later 19th-century cast iron balcony on the first floor, and the return displays similar details. The cast iron area railings have urn finials.

Inside, the building retains an elegant wrought iron staircase balustrade in a top-lit well, as well as a vaulted and apsed anteroom with a Venetian window. The back drawing room on the first floor features painted and stuccoed interiors, along with original door furniture and chimneypieces.