St Columba Church, Sinclair Street, Helensburgh

St Columba Church is a Gothic-style church built in 1860 by William Spence, with offices and a hall added later in the 19th century. The church is rectangular in plan, with a prominent three-stage tower centrally positioned on the east (entrance) elevation, and an L-shaped office block abutting the northwest angle.

The church is constructed of squared, stugged, and snecked cream sandstone with ashlar dressings. It features base and eaves courses, and the windows are pointed-arch, transomed, and hood-moulded, with Y-tracery; the eastern elevation and tower have cusped tracery. Pointed-arch doorways are also hood-moulded, with diagonal buttresses featuring saw-tooth coping and a crenellated parapet along the east elevation.

The east (Sinclair Street/entrance) elevation is three bays, with the central tower having off-set and gablet angle buttresses. The tower's entrance has a slightly advanced doorway with a pair of boarded doors. The tower roof is half-piended, with louvered windows in the belfry stage. Decorative blind pointed-arch tracery and cusped detail are found below a corbel table and cornice, with pierced stonework to the parapet. Flanking the tower are a half-gable bay with a window to the right and a doorway with a small window above on the return to the right, mirrored on the left.

The south (King Street East/side) elevation has five bays, with a taller gabled bay to the right containing two windows and a circular window with quatrefoils in the gablehead, topped with an apex stack. To the left of the taller bay are three windows of the nave, with a door located between the first and second windows. The north elevation is a mirror image of the south elevation. The west elevation features a projecting chancel with a bipartite window on its south side. The windows contain lead-pane glazing, incorporating some small stained glass panels. The roof is covered in grey slate, with cast-iron rainwater goods.

Inside, the church has a vestibule with encaustic tiles and a curved stone staircase leading to a gallery. The U-plan gallery is supported by cast-iron columns with foliated capitals, and features blind pointed-arch and cusped tracery detail on the gallery balcony. The nave ceiling has a plastered, ribbed, semi-circular barrel vault, while the aisles feature coffered panels. A timber rood screen with a pulpit abuts the screen; an organ is located behind in the chancel. A decorative marble baptismal font has winged angles at its base.

The single-storey offices, in L-plan, are built of grey stugged and snecked sandstone ashlar. A three-bay link connects them to the northwest angle of the church, featuring a doorway in an advanced gabled bay to the center, flanked by small windows. Adjoining the link is a wing with a doorway and window in the re-entrant angle, and a taller block to the right with three regular windows. The east elevation of this section is gabled, with a bipartite window central and a louvered oculus in the gablehead. The office windows are 6-pane timber sash and case with frosted glass, and the roof is grey slate with ashlar coped skews, block skewputts, rendered stacks, and moulded cans.