Pyro Building P4 (Carillion Building 59) at Rhydymwyn Valley Site

A very large building of reinforced concrete frame construction with infill of red brickwork laid in English bond. Seven bays to long (east and west) elevations; on lower level of W elevation each bay formerly had 2 openings (ie 14 in all) now blocked. The central section of 5 bays has segmental concrete vault over each bay. At each end a bay with flat roof. The N & S elevations have six bays externally. Square concrete tower to N over second bay from W. Much alteration and blocking of original openings. In S elevations, later insertions of two large vehicle entrances.

The interior is articulated by reinforced concrete posts; some circular openings to roof. Overhead rails for lifting gear. Building is divided longitudinally into 2 areas; to W the toxic area of 3 bays, and to E the non-toxic area of 2 wider bays. At N end of non-toxic side, small single-storey divisions for two transformers and switch room. Remains of switchgear and fire-fighting equipment.