Craig Ddu slate works (nprn 537337) was built in the 1880s at the foot of the upper incline below the quarry. It continued working until 1946. This mill building is 25m N-S x 10m and its walls are built of quarried slate blocks bonded in mortar, mainly reduced to 1m, except for the N gable end which stands 2.3m high and incorporates a doorway.
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H & H, 10/03/2014.