25 Clarendon St., Londonderry

25 Clarendon Street is a mid-terrace two-bay three-storey townhouse with attic over basement, built in 1862-63 in Georgian style. It forms part of a row of twelve similar early to mid-Victorian houses lining the south side of Clarendon Street, located within the Clarendon Street Conservation Area. The building is constructed of red brick in Flemish bond with painted stone and brick dressings, and has a pitched natural slate roof with black clay ridge tiles.

The principal north elevation faces Clarendon Street and sits behind a low rendered wall topped with replacement black painted metal railings. The front entrance is approached by five steps, with the bottom step projecting beyond the boundary wall onto the pavement. The entrance comprises a three-centred-arch opening with moulded cornice supported by Doric order columns, containing a painted timber four-panelled door with a single-pane overlight. To the left of the door are two diminished windows at basement level. The upper floors contain two square-headed windows on each of the first and second floors, with painted cement rendered reveals and painted sills. These upper-floor openings are not aligned with the ground floor windows. All windows are 6/6 timber sliding sash unless otherwise stated. Two basement-level windows are positioned directly below the ground floor windows but are not fully visible from street level.

A large red brick chimney stack with nine terracotta pots rises from the east gable, centred on the ridge. Cast-iron guttering with iron brackets runs along the front elevation, with cast-iron guttering, downpipes and hopper to the rear.

The east and west elevations are abutted by adjoining buildings at Nos. 23 and 27 Clarendon Street respectively. The south (rear) elevation is cement rendered and comprises a three-storey section over basement with a projecting rear return (shared with No. 27) to the left. The right bay of the main block has a basement-level opening and single 1/1 timber sliding sash windows to ground, first and second floor levels, with the second-floor window not aligned with those below. A pitched roof rendered dormer above contains a single top-hung casement window. The left bay is abutted by the rear return; its exposed section has a 3/3 timber sliding sash window. The rear return's south gable contains a single top-hung casement window to basement level and 1/1 timber sliding sash windows to ground, first and second floors. The east face of the rear return was not visible at the time of survey; the west face is abutted by the rear return of No. 27.

To the rear of the site is a two-storey pitched corrugated fibre-cement roofed stone mews building with brick dressings. Its north elevation features a vertically sheeted timber door to the left of centre and a segmental-arched coach arch to the right (altered to a square-headed opening), with two square-headed timber louvered openings on the first floor. The east and west elevations are fully abutted by the mews buildings of Nos. 23 and 27 respectively. The south elevation has a segmental-arched coach arch to the left (altered to square-headed and containing modern vertically sheeted timber doors), a vertically sheeted timber door to the right of centre, and a blocked-up opening further right. The first floor has timber louvered openings above the coach arch and above the door below.