Ysgol Gyfun Bryn Celynnog

Inside the main entrance are half-glazed double doors and a short passage leading to the corridor which runs along the rear of the front range, and continues at right angles behind the N and S wings. The classrooms lead off this corridor. Straight ahead from the main entrance is the assembly hall, now the school canteen and with added kitchen block behind. In the SE corner (between the front and S ranges) is the former office of the head teacher, and in the NE corner a former boiler room, both of which originally had fireplaces. Half-glazed double doors within the side entrances, with small rooms flanking, possibly cloakrooms. Near the centre of the N wing is a small tutor's office, marked externally by a small window, and entered through a boarded door with a small window to its L. Internal detail includes brown glazed tile dado with green banding. The classrooms are mainly unaltered and have half-lit panelled doors with multi-pane lights, adjacent to which are sash windows. The hall, entered through half-lit double doors, is 4-bay, with arched braces decorated with moulded triangles supported on small corbels. Two doors to the rear lead to the kitchen.

Single storey with E-shaped plan in Neo-Georgian style. Long ranges except for the central rear wing, the front facing E. Constructed of red brick with prominent limestone dressings under slate roofs. Red brick stacks to L and R of front range roof pitch. Detail includes a dentilled stone eaves cornice and dentilled pediments. The tall windows rise to the eaves, have stone sills and contain 6-over-6-pane horned sashes with 6-pane ventilating lights above. The front range is symmetrical with central main entrance and advanced gabled bays to the ends. The entrance is within a dressed stone doorcase, 2 Ionic columns in front of piers supporting an entablature inscribed 'Beddau Girls School', above which is a segmental stone pediment. It contains a boarded door with an overlight retaining its original glazing. Flanking the entrance are 4 pairs of windows. The advanced bays are the gable ends of the N and S wings. Triangular pediment to each gable, the string course a continuation of the eaves cornice. Each pediment is broken by an almost full-height round arch. The arches are slightly recessed with gauged brick heads and tall moulded keystones, each containing a window below a stone tympanum. That to the L reads 'Glamorgan County Council, 1928' and bears the county shield, with a ribbon beneath. The R tympanum reads 'Beddau Girls Council School' and the same in Welsh below.

The external N side has a doorcase offset to the L. This has brick piers, a moulded stone cornice with brickwork above, in the centre of which is a stone tablet reading 'Merched', and in smaller writing, 'D Pugh-Jones, County Architect' and 'Richard Jones, Builder, Caerphilly'. Above is a small triangular pediment with brick infill. Within the entrance are double panelled doors with a multi-pane overlight. To the far L is a window, next to which is a smaller 4-over-4-pane sash. In front of these is an enclosure of iron railings inside which a flight of steps leads down to a basement room. R of the doorway are 10 windows as front, except for the 6th window which is very small and under a gauged brick head.

The external S side is mainly as the N side, with a similar doorcase offset to the R, inscribed 'Merched', and the same arrangement of windows to the far R. Fifteen windows to the L, as front. The rear gable ends of the ranges have moulded verges but no openings. Around the rear sides of the front range and N and S wings is a low enclosed corridor now with flat roof and mainly late C20 glazing. Sash windows project above the corridor, lighting the classrooms. The end of the S corridor has double doors. A flat roofed extension joins the end of the N wing and leads to a late C20 school block. The shorter central rear wing is 4-window, each sash and ventilating light of 8 panes, and with moulded eaves. Against its gable end is a later brick extension with a flat roof. Small flat-roofed blocks in angles of front and end wings.