Churchyard, Bonhill Old Parish Church, Main Street, Bonhill

Bonhill Old Parish Church is a hall church dating from 1836, with subsequent additions and alterations. It is built in a Tudor-Gothic style and includes a tower. The church is constructed from coursed pink sandstone ashlar with ashlar margins and dressings. A deep base course is present, along with hoodmoulds, a string course, clasping buttresses, eaves moulding, and chamfered reveals.

The east elevation features an integral, three-stage, battlemented tower. A three-centred arch doorway, with a roll-moulded surround and hoodmould, is centrally positioned at ground level. Above this is a two-light Y-tracery window, with a clock set within a lozenge shape at the string course separating the second and third stages. A three-light window occupies the upper stage, and the upper two stages feature colonetted quoins. A battlemented parapet tops the tower, with octagonal pinnacles. Flanking the tower are buttressed bays, each containing a tall two-light Y-tracery window, and clasping buttresses.

The north elevation has three bays forming a chancel, with a fourth narrow bay to the outer left, each featuring two-light Y-tracery windows. The south elevation mirrors the other elevations with four bays, but incorporates a modern addition at the centre, which is a full-height, piend-roofed structure with chamfered corners, rendered and featuring reconstituted stone dressings. A pointed arch doorway is present on the return, alongside lancet windows.

The west elevation has a broad gable, originally with three lancet windows, now featuring a later gabled red brick bay advanced at the centre. A sandstone quatrefoil is at the centre of the gablehead. A 1930s flat-roofed vestry block is situated at ground level, rendered with cement margins.

The interior has been significantly altered, with the church reduced in size due to the creation of additional offices and meeting rooms. The original main entrance no longer serves the church. Some original church furniture remains, including a communion table, and a new gallery has been installed. Stained glass windows commemorate Alexander James Dennistoun Brown of Balloch (1885) and Alexander Smollett of Bonhill (1881). Stained glass on the stair to the hall depicts Rachel Sword Kippen and William James Kippen of Westerton and Busby, designed by Robert Milligan of Glasgow in the 1940s. Several interesting grave memorials are located in the churchyard, including an engraved slab stone dedicated to the covenanter Robert Nairn, who died in 1685. The burial enclosures against the south boundary wall are of particular interest, including The Arthurs of Levenbank Mausoleum dating from 1797, a Classical pink sandstone ashlar structure with a pedimented front featuring fluted pilasters and no roof. The Turnbull Mausoleum, also roofless, incorporates stugged sandstone ashlar, a segmental-headed door with a blocking course, triangular section pillars, an angel sculpture, and remnants of acroteria. The Buchanan of Ardoch Mausoleum, dated 1798, is Classical, with a segmental-headed doorway, a triangular pediment, and an inscribed plaque. A Venetian Gothic gabled burial enclosure stands along the east boundary wall.

The boundary wall and gatepiers are constructed from low stugged red sandstone rubble with harl-pointing, and are topped with semicircular coping.