Lansdowne House, including the cellar which forms part of the basement flat to Cerberus House, and the attached railings

Lansdowne House is a late 18th-century former townhouse, converted to an office and residence in the early 19th century, later used principally as an office before being converted back to residential use after the 1990s. The cellar beneath the house forms part of the basement flat to the adjacent Cerberus House and is included in this listing. The attached railings to the front of the building are also listed.

The building is constructed of red brick with blue-brick and stucco detailing, and has hipped concrete-tile roofs. It is a three-storey townhouse with cellar and attic levels, with a rectangular footprint orientated east to west and a stair tower projecting to the rear.

The front elevation is a six-window facade in exposed red brick laid in Flemish bond. Blue-brick string courses run above the ground and first floors, with a stucco cornice below the stucco parapet; behind the parapet are a large and small hipped roof. The off-centre entrance door is reached by small steps and is topped by an arched overlight. The door case comprises a pair of Doric columns supporting a broken entablature and pediment, with panelled reveals. The six-over-six sash windows are topped by flat-segmental arches with brick voussoirs. To the left of the elevation is an early 21st-century basement window set within an earlier opening. The east elevation is rendered, while the west and rear elevations are brick. The projecting rear stair tower is topped by a parapet.

Internally, the house follows a single-pile plan with rooms arranged either side of an off-centre hallway containing a dogleg staircase that rises through the building. The staircase has a curtail base step, open string, and a timber bannister with moulded handrail and decorative balustrading featuring stick and barleycorn spindles, supported by additional metal bracing. Stepped architraves with tall plinths appear to be original throughout the building. The ground and first-floor windows retain their panelled shutters and reveals. Several rooms on the ground and first floors have classical-style fireplaces, and some retain early skirting dado rails, cornices and ceiling roses, though others were replaced particularly in the 1990s. The ground-floor east room has a panelled wainscot, part of which has been replaced in recent years. A further fireplace with surround is located on the second floor. The barrel-vaulted cellar beneath the central brick range was incorporated into the basement flat of Cerberus House in the early 21st century.

Flanking the front door are two sets of early 19th-century spear railings on low masonry walls.