Two single storey buildings built with long sides facing each other, each of two phases and constructed between 1870 and 1897. Both mills are orientated E-W. The space between the two parallel sided buildings is spanned by a flat roof. The Southern Mill is 0m x 0m. Constructed of coursed slate blocks, with a pitched slate roof of shallower pitch on southern side and hipped at W end. Skylights inserted into roof at regular intervals. Mill machinery in both mills originally powered by a 12m diameter overshot waterwheel which was inserted into the building parallel to the pitch of the roof. This wheel was still in place in 1924 (photograph) and 1939 (plan) and was removed by 1946 and the opening in the roof slated over. A photograph dating 1889 ? 1900 shows a drive shaft exiting the southern mill through a gable end and through a series of bevel gears, entering the northern mill through a hole provided in the gable end.

Internally the roof of the Southern Dressing Mill is constructed using King Post roof trusses and the building floor space is divided into working areas for processing and dressing the slate. In situ next to the W supporting wall of the Water Wheel are an Air Compressor and associated horizontal compressed air storage tank (sitting on temporary breezeblock supporting walls and appearing to replace in earlier installation of similar type) with pipe work leading from the tank to an exit under the southern eaves.

The Southern Dressing Mill was decommissioned in 1969 and the majority of the slate processing machinery and temporary interior diving walls were removed, although the machinery driveshaft in the roof space and the tramway rails were left in place.
The Northern Mill is approximately 0m x 0m. Constructed of coursed slate blocks, originally with a gable roof at the E end, with a later monopitch extension added to the E end prior to 1897 to create a hipped roof. A plan of 1918 names the section of mill parallel to the Water Wheel in the Southern mill as `Engine House?.

Internally the roof of the Northern Mill is constructed using King Post roof trusses and has skylights let in at regular intervals. Internally the building is divided into working areas for processing and dressing of slate, and a conveyor belt runs along the length of the northern wall of the building. Belt driven machinery from a driveshaft running along the length of the building. Temporary walls raised on northern side to separate the working compartments (gwaliau) are intact. The Northern Mill was decommissioned in 1999 and the majority of the slate processing machinery left in situ, as were the tramway rails and the machinery driveshaft in the roof space.

References: Plans referred to are held by J. W. Greaves and Sons Ltd, Blaenau Ffestiniog

Spencer Gavin Smith, RCAHMW, August 2011