The new engine house for the Maenofferen Slate Quarry locomotive stock was constructed after 1939 according to plans held by J. W. Greaves Ltd and replaced an earlier engine house (NPRN 415949) situated next to the tip run (NPRN )to the north of the River Bowydd. The new engine house was situated south of the River within the main mill complex north of the workshop range. It comprises a single storey building orientated N-S and measuring 6.7m x 5.1m externally, with a double door offset of centre in the N wall, 2 windows in W wall and single door in W corner of the S wall. It is constructed of coursed slate blocks with walls 0.6m thick and has a pitched slate roof. Inside there is a 3.8m long by 0.7m wide plinth along the west wall. The new engine house was decommissioned in 1999 and a tank wagon left in situ on tramway tracks inside the building.

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

Louise Barker & Spencer Smith, RCAHMW, August 2011.