St Mary's Church, 31 Dunderg Road, Macosquin, Coleraine, Co. Londonderry, BT51 4NE

St Mary's Church is an early nineteenth-century blackstone Gothic Revival parish church situated on the south side of Dunderg Road in Macosquin. Built in 1827, it comprises a rectangular plan with a square three-stage entrance tower to the west, chancel and vestry added in 1867 to designs by Welland and Gillespie. A modern entrance lobby abutts the south face of the tower, connecting the former Sunday school to the west.

The building is constructed of random rubblestone, squared and brought to courses at the tower, with part ribbon pointing and sandstone dressings throughout. The pitched natural slate roof features blue and black angled ridge tiles, with raised sandstone verges to the vestry. Plastic rainwater goods are fitted.

The nave and chancel are lit by bipartite leaded-and-stained windows with cusped tracery in blocked sandstone surrounds with chamfered reveals and sills, surmounted by hood moulds with plain square stops. Many nave windows are replacements. The vestry and west face of the tower feature pointed-arched margined diamond metal lattice lights in chamfered sandstone surrounds with splayed sills; the tower's west-facing lattice lancet is surmounted by a hood mould with plain stops.

Buttresses with masonry offsets flank the nave, whilst the chancel is detailed with sandstone quoins. The square tower rises to a crenellated parapet with corner pinnacles. The belfry features louvered lancets with hood moulds on all four sides. A Roman numeral clockface is set within a sandstone roundel to the second stage on the north and west faces. The south face of the tower contains a square four-pane timber window. At ground floor level on the west face is a lattice lancet and a sandstone datestone inscribed "1827". The west-facing gabled front is abutted at centre by the tower, with a window to the left. A modern pointed-arched timber-sheeted door with blackstone voussoirs provides the principal entrance at the base of the tower.

The gabled chancel (1867) projects from the east gable and features a window with three-light cusped tracery. The vestry extends around the right cheek of the chancel and along the north side of the nave, lit by a lattice lancet to its east gable and two further lattice lancets to the north. Access to the vestry is via a timber-sheeted door with shouldered head in a sandstone blocked surround, accessed by two stone steps on its west cheek.

The church stands within a cemetery setting on a square plot. To the south side of Dunderg Road lies the main cemetery, containing a variety of headstones dating from the early nineteenth century. A burial plot to the north side of the church is enclosed by rubblestone walls with sandstone coping topped by cast-iron railings with fleur-de-lis heads and a gate, containing two nineteenth-century headstones. The site is bounded on three sides by random rubble walls, partly dry stone, with a rubble stone wall featuring sandstone coping and part replacement cast-metal railings to the front. Square sandstone piers support replacement cast-metal entrance gates. A rubblestone single-storey hall stands directly to the west.