Derg Parish Church, 13 Main Street, Castlederg, Co Tyrone, BT81 7AY

Derg Parish Church is a detached double-height Church of Ireland building dated 1731, located on the west side of Main Street in Castlederg. The church consists of a rectangular nave with a square tower to the west, possibly built on the remains of an earlier seventeenth-century tower. A northern aisle was added around 1870, followed by a gabled chancel to the east and a single-storey lean-to extension with cat-slide roof, both added around 1905. A single-storey flat-roofed vestry extension to the north-west was added in 1971 and is of little architectural interest.

The roofs are pitched natural slate with blue and black clay ridge tiles, raised stone verges, bead moulded kneeler stones, and exposed timber rafter-ends to the north aisle. Chimney-stacks rise from the gables. The main walls are ruled-and-lined rendered with chamfered quoins over a projecting plinth; the tower has roughcast facing. The north aisle features roughly coursed rubble with ashlar sandstone quoins, while the chancel is constructed of squared-and-snecked rockfaced sandstone with ashlar quoins.

Windows throughout are round-arched-headed, containing leaded stained glass and surmounted by hood moulds with moulded stops and sandstone sills. The north aisle windows have stepped sandstone surrounds with chamfered sills and no hood moulding. The principal elevation faces south and is five windows wide. The west gable is abutted at its centre by a stepped two-stage square tower containing a single window at the first stage.

The south elevation contains replacement round-arched-headed double-leaf timber panelled doors in a sandstone architrave, flanked by replacement sandstone columns surmounted by a frieze inscribed with a Latin dedication dated Anno Domini 1731, commemorating Hugo Edwards and the support of Bishop Henry Downes and Parochial Rector Robert Downes. Above the frieze is a broken pediment containing a coat of arms. The second stage of the tower contains a single round-arched-headed louvred opening to each elevation and is surmounted by a crenellated parapet with stone finials at the corners.

The south elevation is abutted on the left by a gabled aisle containing a tracery rose window surmounted by a hood mould with label stops and rubble voussoirs. The north elevation is abutted by the five-window-wide aisle and at ground floor by the lean-to extension, which contains a single square-headed window. A stepped ashlar chimney-stack rises from the party wall with the aisle. The west elevation contains a single window, and the east elevation features a round-arched-headed vertically-sheeted timber door in a bead moulded architrave surmounted by a stained glass oculus.

The east gable is abutted at its centre by a gabled chancel containing a large pointed-arched-headed geometrical tracery window surmounted by a hood mould with decorative label stops and rubble voussoirs. A wall-mounted memorial plaque dated 1759 is positioned on the south elevation of the chancel. To the right, separated by a rubble buttress, is a gabled aisle containing a large pointed-arched-headed plate tracery window surmounted by a hood mould with label stops and rubble voussoirs.

The church is set within a churchyard containing grave markers dating from the early eighteenth century to the present day. The site is bounded to the road at the east by a rubble plinth wall with stone coping surmounted by cast-iron railing. Access is provided through smooth rendered square pillars supporting a pair of cast-iron gates at the north-east and a single gate at the south-east. Cast-iron ogee profile gutters and square downpipes are fitted throughout.

To the north-east stands a four-bay two-storey parochial hall constructed of roughcast and red brick, accessed directly from the street and largely modernised in recent times.