The Old Mill, Engine House and Boiler House at Stonebridge Mill

The Old Mill, Engine House and Boiler House at Stonebridge Mill is a fulling, carding, and scribbling mill built around 1800, with alterations made in the mid 19th century and 20th century. The structure is made of coursed gritstone rubble, partly rendered, with ashlar dressings. The roof is partly slate, featuring glazed roof lights, and partly covered with corrugated sheeting.

The mill stands three storeys plus an attic and has nine windows. The north-west gable front has much of the ground floor obscured by later additions, featuring a single late 19th-century window to the right. Above this is an off-centre doorway with double doors, flanked by single 2-light windows, and a further window to the left. Above are four 2-light windows, all with raised ashlar surrounds, and another later window above.

The south-east front has seven bays, with the left bay obscured by a later lift shaft. To the right is a large plank door with an overlight, and to the left are four 2-light windows. Above these are four similar windows and an enlarged window, followed by five more 2-light windows. All these openings have raised ashlar surrounds. The north-west front is similar, featuring eight windows.

The engine house, attached to the south-west, dates from the mid 19th century and has a three-storey gable front to the north-west, with a double panel doorway and an upper round-headed window with a raised ashlar surround, set within a round-headed sunken arch with a continuous impost band. Above is a single round-headed window, also with a raised ashlar surround. The boiler house, also attached to the south-west and from the mid 19th century, includes drying rooms above. Beyond are two lean-to buildings, including an in-built Wagon Boiler used as a water tank, and a tall square stone chimney stack that served the engine house.

Inside, the mill features wooden cross beams and floors supported on circular iron columns, with fixtures for line shafting. The roof is supported by wooden trusses.