Post Office, 3 Custom House Street, Londonderry, Co. Londonderry, BT48 6AA

This Classical-style post office was built in 1876 and is constructed of rock-faced 'block-and-sneck' Barony Sandstone with cement strap pointing and cut-stone dressings to openings, all set on a moulded stone plinth. The building has an L-shaped plan form with a hipped slate roof that is treated as a single composition with the adjoining Custom House building to its east side.

The principal elevation faces south onto Custom House Street and features a distinctive asymmetric layout combining semicircular arched headed window bays with segmental arched headed grouped window bays. The building occupies a prominent corner site overlooking Harbour Square and Queens Quay to the east, positioned within a characterised group of three blocks with street frontage that creates a coherent architectural composition overlooking the River Foyle beyond. The south elevation is stepped, merging with the Custom House facing onto Custom House Street.

The main entrance faces east and is accessed via a short flight of concrete steps and ramp from Custom House Street, set behind a high sandstone wall with coping stone. Large semicircular arched headed window bays occupy the ground floor level, featuring deep chamfered reveals and angle-roll detailing to the arched head above, with slightly projecting stone string-courses between bays. Windows on the floor above are segmental arch headed and set within deep reveals with ashlar cut-stone dressings and angle-roll to the arched head. Stepped corner ashlar quoin stones terminate either end of each elevation on the moulded stone plinth. A large carved stone modillion cornice with deep projection runs at eaves level, surmounted by cast-iron guttering.

All upper-floor windows are 1/1 timber sliding sashes, whilst ground floor windows are timber casement windows with bottom hinges. The west elevation faces onto a rear access yard overlooking the Northern Counties building and features four windows to ground floor level and four above, replicating the fenestration pattern and material finishes of the south elevation, including identical plinth, facade, and eaves detailing.

The north elevation is abutted by a yellow brick three-storey extension with a hipped slate roof that merges with the main roof on the west end. The north elevation on the east end is also abutted by an L-shaped red brick three-storey extension with cast-iron segmental headed windows, gable-ends to east and west sides, and a single-storey extension on the north side featuring a hipped glazed roof light. The red brick extension has brick piers between segmental arched headed openings on concrete unpainted sills, with exposed rafter tails to timber soffit and fascia board at eaves level, all on a concrete unpainted plinth with uPVC rainwater goods. The yellow-brick three-storey extension has square-headed uPVC casement windows, with metal grilles to ground floor windows and uPVC rainwater goods throughout.

The east elevation faces onto Harbour Square and contains a large semicircular arched headed entrance doorway, accessed via a flight of steps and ramp from Custom House Street. The opening features ashlar cut-stone dressings with chamfered reveals to either side of a modern automatic metal door with glazed panes top and bottom, set within a plain timber architrave surround. Above the door is a plain glazed transom light and a plain glazed fanlight to the arched opening with angle-roll to the chamfered arched head. A segmental arched headed bay above the entrance, aligned with the door below, contains a 1/1 timber sliding sash window.

The hipped slate roof features a lead rolled ridge, with the west end block having a central projecting hipped roof with rendered sides over the main banking hall. Large stone chimney stacks with stone cornices are positioned mid-ridge of the south elevation and to the east elevation, each with four clay pots. Cast-iron rainwater goods serve the principal Post Office building, whilst uPVC goods are fitted to the north end brick extensions.

The building is positioned adjacent to the west side of the Classical-Italianate Harbour Office, within a prominent group of three blocks along Queens Quay with excellent street frontage. This grouping creates a characterised and architectural composition overlooking Harbour Square and the River Foyle to the north, bounded by the Guildhall to the east and adjoined to the former Customs House to the west. A double Elizabeth II post-box is located in front of the main facade.