18 Church Square, Rathfriland, Newry, Co Down, BT34 4PT

18 Church Square is a two-storey, one-bay shop dating to around 1874, set within a terrace on the east side of Church Square in Rathfriland. The building is of rendered construction with a pitched artificial slate roof that continues over the adjacent property to the right. A rendered chimney rises from the left gable, and half-round metal guttering with a downpipe sits to the left of the façade, with plastic ogee gutters serving the rear.

The front elevation, painted render with an advanced eaves course, is dominated by the shopfront, which remains the only element of architectural interest. The ground floor comprises a symmetrical timber shopfront with a slightly recessed central doorway. The door is modern, sheeted timber with a top glazed panel, but retains an original two-paned transom above with semi-elliptical heads to each pane and incised spandrels. On either side of the doorway are shop windows, each divided horizontally by a timber glazing bar. The upper portion of each window has three tall fixed panes with thin timber glazing bars between them; each pane has a semi-elliptical head with incised spandrel matching the transom design. The lower half of each window now contains a single large pane, though it is likely that three panes originally existed here too. Both windows have projecting painted timber cills. Flanking the doorway and framing the outer ends of the shopfront are tall, thin moulded timber pilasters resting on painted granite base blocks. The pilasters feature a small abacus and moulded timber heads (the left example has been lost and replaced with plain timber). They support a plain painted timber fascia, now covered by a modern plastic panel bearing the inscription "D McDowell / Confectionery – Accessories / FILLING STATION". Above sits a run moulded cornice in painted stucco.

The first floor contains two 6/6 sliding sash windows without horns, each with exposed boxes and painted granite cills; much of the original crown glass survives. A modern security alarm box is positioned between the windows at cill level. Electrical cabling crosses the façade at eaves level.

The left gable abuts a taller adjoining building, while the right gable forms a party wall with the adjacent property. The rear elevation is lime-rendered rubble stone, now mostly deteriorated. At ground floor, the rear is largely obscured by a modern single-storey return in concrete blockwork with a shallow monopitched corrugated metal roof. Two brick-dressed windows with granite cills exist in the main wall—one between ground and first floor on the left, and one at first floor level on the right—both now infilled with concrete blockwork. The modern extension has a flush plywood door to its rear gable and two small modern casement windows on its left cheek facing the coachway of number 20 Church Square; its right cheek is blank and abuts the yard wall of number 16. A large linear yard extends to the rear.

The site was built over in 1776, but the present building and its southern neighbour were constructed around 1874, as indicated by the Valuation revision book. The building operated as a petrol filling station with a single pump to the street, known locally as Dougie McDowell's, until closure in April 1999 when roadside petrol pumps became unlawful.

The rear and interior retain no features of architectural interest.