Church comprised of 3 building phases of 1864, 1882 and 1910. Existing church now consists of 2 aisles, 5 bays from N to S, giving approximate cruciform plan with sacristy at N end. Original church and (2nd phase) aisle oriented E/W at S end of (3rd phase) later building. Principal floor entered at street level from George street. Site slopes down to basement floor level at rear (W) of building. Grey stonework of earlier phases painted to match red squared and snecked sandstone of 3rd phase.
1ST BUILDING PHASE; original parish church by J Thomson of Glasgow 1864, simple rectangular plan in plain gothic style. 3-light geometric traceried E window supporting roundels, stained glass, retained in east side aisle at rebuilding of 1910, as gable, breaking eaves. Gable contains 2 stained glass lancets and rose window with stained glass in outer lights. Angle buttress at corner. Simple, pitched, grey slate roof, N pitch and corresponding structural timber below removed, replaced with flat roof connection to 1910 building. Now functions as rear of nave to later church. S facing porch at E end obscured by later
porch leading into 1882 side aisle. Corresponding porch of 1864 phase at W end of N wall, buttressed, with iron cross finial and ornately hinged timber 2-leaf doors.
2ND BUILDING PHASE 1882: side aisle addition to S of above, simple rectangular plan in plain gothic style. Entrance porch with buttress, pointed arch doorway and hoodmould above attached to E gable wall with rose window, hoodmoulded, and iron cross finial above. S wall of 5 bays, single lancet in each. Angle buttresses at corners. Simple pitched grey slate roof, plain console at end of skew cope. Now functions as narthex and baptistery. Divided from nave by glazed screen with doors, Ian G. Lindsay & Partners 1958.
3 BUILDING PHASE; James Chalmers of Glasgow 1910, proposed cruciform plan, with W transept, W side aisle, and S end of nave remaining unbuilt. Plain Romanesque style with round-arched windows, triple window in E wall of transept with vesica above. Grey slate, pitched roof with rooflight over crossing instead of proposed tower. Cornice of square moulding and masks at eaves. Buttresses, angle buttresses at corners. 1 bay of nave arcade built, with circular columns supporting
round arch, with round arch, stained glass window above. Window on E side infilled behind glass. Shallow W aisle containing stairs to pulpit. Pulpit, Romanesque style, circular with 3 main arches containing 2 subordinate arches, red sandstone, decorated with onyx, alabaster and marble. Crossing arches to E and W extant, arches to N and S unbuilt. Columns for N and S arches support recent structural steelwork. W archway infilled with masonry, backdrop to eagle sculpture and bishop's stall.
Choir stalls and 2 lecterns, raised granolithic floor accessed from
nave by 3 white and green marble steps. Low wall to either side in pink sandstone with yellow marble cope. Organ by Blackett & Howden of Glasgow, within E crossing arch, supported on 3 arches on octagonal columns. Springers for corresponding arches in W crossing. Decorative relief panels on organ case. Chancel accessed by green and white marble step to granolithic floor. 6 further green and white marble steps to high altar. Timber reredos above sandstone frame decorated with carved cherubs heads and lugs, inset with coloured marble panels.
Octagonal pedestals above with sandstone sculptures. Piscina, and sedilia of 3 seats in single round arched recess, in E wall of chancel. Romanesque arch of single order with Bishop's crest set in W wall of chancel.
Lady Chapel (E transept) north wall supported on round arch supported in turn half-round columns on rectangular corbels. N wall beyond has rectangular recess as reredos to yellow marble altar. Doorway in Romanesque style arch to left of altar. Low brass screen decorated with grapes, surmounted with timber handrail.
Lady chapel, nave, and chancel ceilings lined with timber strips in
barrel vault form. Internal stonework of stugged, squared and snecked pink sandstone, droved ashlar on dressings, columns and details.
Basement lit at George Street front by narrow area protected by