Penallta Colliery was built by the Powell Duffryn Steam Coal Company in 1906-09 and was one of the last steam-powered collieries constructed, although it did also generate its own electricity. In 1910 huge difficulties were experience while opening out the Red Vein due to faulting. By the early 1930s the colliery employed over 3,000 and was achieving an annual production figure of over 860,000 tons.

Its layout was the model for subsequent collieries, with one common engine-hall (NPRN 85090) measuring 91.4 metres by 21.3 metres (300ft by 70ft) to replace the previous separate engine-houses that adjoined each shaft. A large workshop building (NPRN 85284) in a similar style lies alongside.

The Number 1 and Number 2 shafts of 6.4 metres (21ft) diameter are respectively 713.2 metres (2,340ft) and 687.6 metres (2,256 ft) in depth. The winders were made by Fraser & Chalmers, the Number 1 spiral drum is 4.57 m ? 7.3m (15ft - 24ft) with a double tandem Corliss compound engine. Number 2 has a 4.57 m (15ft) drum with a Corliss cross-compound engine. Ventilation was by a Sirocco fan of 3.9 m (12ft 10in) diameter, driven by a Davey-Paxman high-speed compound and a 550 horsepower Westinghouse motor. The engine house also housed 23 MW turbo-generators, two compressors and a compound generator. The fan casing was on the eastern end of the hall.

The large engine-hall retained its Art Nouveau-style tiling although it was largely re-equipped in the 1960s. Adjacent to the engine-hall are twin headframes (NPRN 85295, NPRN 85296) built in 1906 using steel joist construction and nearby are 1930s baths (NPRN 85292) built by the Baths Welfare Committee Architects in an early version of one of their standard designs. This contrasts with the pilasters, string courses and eave courses in red brick which decorate the sandstones of the Edwardian buildings.

Although the pit closed in 1990 and the buildings and headframes have been retained. The 81m by 14m (266ft by 46ft) workshops, lamp room and offices, the oil and general stores and locomotive shed also survive although the boilerhouse and chimney have been demolished.

B.A.Malaws, RCAHMW, 11 February 2009

& Claire Parry, RCAHMW, 23 June 2011
Source: A Guide to the Industrial Archaeology of South East Wales, AIA, 2003