This extremely elegant apartment , entered from a door on the first-floor landing, is part of the 1736 house. It must have served as a more intimate drawing-room alongside the large, formal saloon with which it interconnects. The door-cases are coeval with the room. They display Richard Castle's design at its best - masculine and assertive, each line charged with energy. The architrave is massively framed and shouldered and broken through by a dentil cornice. The wood is West Indian mahogany of the highest quality, used to lavish advantage by its joiner.
This material had only become generally used in Ireland in the late 1720s and Castle was among its champions He used it in Dublin at Leinster House and Tyrone House and at Russborough, Co. Wicklow. But as these buildings post-date Bishop Clayton's house the Iveagh House doors may be his first use of the material. The doors retain their original engraved brass lock-plates.
The most important feature of the room is its ceiling which must date, like the frieze in the old dining-room below from after 1766. Its design is transitional. Roccoco animation is frozen and its forms are governed by a tranquil poise which anticipates the neo-classical style of the 1770s. The ceiling is basically symmetrical in design. It bears musical instruments suggestive of chamber music - a French horn, a recorder, a flute, and musical books.
The room was probably used for music making in the 18th century, and at the time of the 1939 sale was known as a music room. The intertwining arabesques, swags of flowers, and trilling birds are typical of earlier Dublin rococo work, and the frieze, as in the room below, is treated differently on each wall. The modelling of the plasterwork is admirably shallow and elegant. The insertion of the ceiling was only the first of several remodellings of the room. In 1866, new windows were installed and a door was driven through the wall on the left of the chimney-piece.
About 1880, Fuller inserted an Adam-style fireplace, replaced in the 1960s by an elegant fireplace of c. 1790. The floral carpet is to a design of Raymond McGrath.