In 1975 Melin Adda was a roofless two-storey stone shell with a cellar, and with large regular windows and brick lintels, probably of mid-nineteenth century date. The interior measured 7.9m by 5.5m, and the walls still stood to 6.8m high. The wheel-pit on the north-east gable would have accommodated an overshot wheel 4.25m in diameter by 1.35m wide. The Afon Goch feeds and flows through a series of ochre beds and the valley was covered in orange oxides.

The building has since been demolished, and there are no visible traces. The mill was probably worked in conjunction with the adjacent windmill (NPRN 40355), and there was a second watermill immediately to the east-north-east of the first one.

W J Crompton, RCAHMW, 18 June 2008.