Pyro Building P6 (Carillion Building 45) at Rhydymwyn Valley Site

The Pyro Building P6, also known as Carillion Building 45, is a very large structure built with a reinforced concrete frame and infilled with red brickwork laid in English bond. It is similar to the Pyro buildings P4 and P5 but is reversed by 180 degrees. The building features seven bays on the long east and west elevations; the lower level of the east elevation originally had two openings per bay, totaling 14, which are now blocked.

The central section consists of five bays, each covered by a segmental concrete vault, with flat roofs at each end. The short elevations have six bays, and there is a square concrete tower on the south side over the second bay from the east. The building has undergone significant alterations, including the blocking of original openings.

Inside, the space is defined by reinforced concrete posts, with some circular openings in the roof. Overhead rails are installed for lifting equipment. The interior is divided longitudinally into two areas: the western area consists of two wide bays, while the eastern area has three narrower bays that have been subdivided into laboratory and office spaces. There are marks on the floor indicating the bases of gaseous diffusion machinery. At the southern end of the western area, there is a small single-storey division likely used as a switch room. Steam air heating ducts are located against the north and south walls at the upper level.