One of two engine houses, with engines in situ, at Glyn Pits Colliery near Pontypool (NPRN: 33566). The earlier engine house (NPRN: 33729) bears a date of 1845 and contains a beam engine, probably by the Neath Abbey Ironworks. This engine house is later. It is not mentioned in an inventory of 1852 but was in existence by 1865. It contains a vertical winding engine of unknown manufacture and is of the house-built type, that is with the engine incorporated in the structure of the building as a single build. It is situated to the east of the two pit shafts (NPRN: 405686) and was erected to take over the winding functions formerly performed by the earlier engine, which up until then seems to have undertaken both winding and pumping. The building has walls of dressed masonry, which are capped with a projecting plinth of two stages. Originally it had a pyramidal roof of slates on timber but this has now gone. The west elevation has, at high-level, a semi-circular opening with soldiered voissoirs and a cast-iron sill. Below this is a pair of semi-circular headed full length openings. The north elevation has a semi-circular headed doorway flanked by square-headed windows. Above a pair of square-headed windows flanks a small semi-circular headed opening. The south elevation has at high level, a small, squat semi-circular headed opening with a cast-iron sill. The west elevation has no openings; a chimney stack, now demolished stood on this side, detached from the building. The semi-circular openings all have soldiered voissoirs. The square-headed windows have dressed stone lintels consisting of a single wedge-shaped block either side a slightly proud keystone, and projecting stone sills. All openings are now blocked.

The engine has a single cylinder of about 36ins. diameter and 66ins stroke and Cornish double-beat equilibrium valves that were operated manually. The slide bars and crosshead were held in an engine frame on top of the cylinder, made of fluted cast-iron columns. The engine drove overhead winding drums of heavy cast-iron construction, which used flat ropes rather than the more usual round section.

A detailed survey of the colliery was carried out by RCAHMW during 2005-2006.

Sources
Tilley, G 2005 The Surviving Engines of Glyn Pits, Pontypool: Early Steam and Water Power in Local Industry.
Palmer, M & Neaverson, P 1990 `The Steam Engines at Glyn Pits Colliery, Ponypool: an Archaeological Investigation'. Industrial Archaeology Review: 13, 7-34.

David Percival & Louise Barker, RCAHMW, March 2007.