Capel y Trinity, including attached former Sunday School and forecourt gates and railings

Capel y Trinity is a tall gable-end chapel in a spare modern idiom, with limited Romanesque detail confined to the entrance front but otherwise austere and functional in design. The walls are roughcast over a brick plinth, with reconstituted stone dressings, and the roof is tiled with projecting eaves. Windows throughout are small-paned with metal glazing bars and tile sills.

The entrance front features a round-headed doorway in a finely moulded deep surround of reconstituted stone, containing double fielded-panel doors beneath an overlight with a radiating iron grille. The doorway is flanked by small windows, and above it sits a round window also fitted with a radiating iron grille. The side walls each have six windows: five tall windows light the main chapel and one, set back, lights the top of the stairs. Projecting flat-roofed aisles have six broader windows with tile drip moulds, of which five light the main chapel and one lights a rear room. A narrower window lights the vestibule. At the rear is a narrow full-height projection containing the organ, which at ground level has a brick section with small windows to toilets and a rear doorway.

On the right-hand side a low flat-roofed link connects to the earlier Sunday School, set forward from the main chapel. The Sunday School also has roughcast walls on a brick plinth with freestone dressings and sills, under a tiled roof. The gabled entrance porch contains a blind pointed doorway, with the steeply-pointed double boarded doors positioned in the right side wall. The blind arch has a hood mould similar to hood moulds of flanking square-headed cross windows. Above is a narrow pointed vent below a smooth-rendered triangular section rising to the apex, which bears an inscription recording the building of the Glanmor Sunday School in 1925. The side walls are plainer: on the left are two cross windows in front of the link from the main chapel, and on the right-hand side are four cross windows. At the rear is an L-plan kitchen and a boiler house in the basement of similar materials, with a brick ridge stack. External steps on the north side lead to the kitchen, and a boarded door to its left opens to the boiler room. Windows on the south side facing the chapel are wide and wood-framed in the boiler house but replacement uPVC in the kitchen above.

To the front facing Glanmor Park Road and on the south side facing a pedestrian alley are railings set on a dwarf wall and between piers, both of brick with concrete copings. The chapel entrance has outer piers of reconstituted stone, between which the fence curves round to similar gate piers inscribed "Capel y Trinity", with iron gates of abstract square pattern. The former Sunday School entrance has more conventional double iron gates with dog bars.

The chapel has a conventional plan comprising an entrance vestibule, galleried main chapel, and rooms behind. In the vestibule, a two-light window with frosted glass opposite the entrance provides borrowed light from the chapel. Doors to the right and left open to the main chapel, and on the right side a dog-leg stair leads to a landing with tiled floor and gallery doors to right and left. At landing level are triple two-light small-paned windows into the main body of the chapel.

The main chapel strikes through its austere stylistic harmony, enhanced by the limited colour scheme of building materials and furnishings. The walls are faced in pale brown brick with smooth render to plain square piers that form a low arcade between main chapel and aisles, beneath a ceiling of square white tiles. Behind the pulpit is a full-height bay of oak panelling incorporating metal grilles through which organ sound was filtered. A raked gallery with a front of coarse concrete faces the chapel space. Oak panelled benches fill the chapel and are reached from the outer aisles, with no central aisle. A wide sedd fawr (principal seat) sits on a raised platform, followed by a canted boarded pulpit with bronze railings.

Most of the building has parquet floors. The chapel's interior doors are single-panelled, but doors in the vestibule and former Sunday School are glazed with small panes. To the right and left in the rear wall are simple panel doors opening to two rear rooms and a corridor with toilets. From the vestibule, the lower flight of the gallery stair is open to the link between chapel and former Sunday School. The former Sunday School retains a boarded wainscot, and its original roof is concealed behind a modern false ceiling.