Pyro Building P5 (Carillion Building 50) at Rhydymwyn Valley Site

The Pyro Building P5, also known as Carillion Building 50, is a very large structure built with a reinforced concrete frame and infilled with red brickwork laid in English bond. It features seven bays on the long east and west elevations. On the lower level of the west elevation, each bay previously had two openings, totaling 14, which are now blocked. The central section consists of five bays, each covered by a segmental concrete vault, while the end bays have flat roofs. The north and south elevations present six bays externally, and there is a square concrete tower on the north side above the second bay from the west. The building has undergone significant alterations, including the blocking of original openings, and the south elevation has later additions of two large vehicle entrances.

Inside, the space is defined by reinforced concrete posts and features some circular openings in the roof. There are overhead rails for lifting equipment. The building is divided longitudinally into two areas: the western section contains three bays designated as the toxic area, while the eastern section has two wider bays that are non-toxic. At the northern end of the non-toxic side, there are small single-storey divisions for two transformers and a switch room.