Spinning Block, Turnbridge Mills (Hirst's Mill)

The Spinning Block at Turnbridge Mills, also known as Hirst's Mill, is a cotton mill spinning block built between 1871 and 1873 to designs by John Kirk and Sons. It remains in commercial use and exemplifies utilitarian design with Italianate influences.

The building is constructed of coursed, dressed sandstone with slate roofs. It comprises a rectangular main block with a projecting stair tower at the south-west corner and a smaller projecting tower to the south elevation.

The Spinning Block is a tall structure of six storeys with an additional basement storey at canal level on the east side. Each storey gradually diminishes in height from ground to sixth floor. The north and south elevations display regular fenestration of eleven bays, the east elevation (facing the canal) has six bays, and the west elevation has four bays. Windows throughout are predominantly vertical rectangular openings with five and six pane timber frames, though some feature louvred panes and others have been replaced with uPVC units or modified as doorways. Each storey is defined by a thin projecting ashlar stone band at window sill level, with stone lintels incorporated into flush ashlar bands linking windows across each façade.

The south elevation features a shallow projecting tower in its centre, with the stone floor bands of the main façade continued across it. This tower has slim windows on its east face and bay windows to its west. Its cornice sits higher than the bracketed eaves cornice of the main block, and an attic stage in stone with plain cornice crowns the composition. Near the top stage is a panel inscribed with the initials of Reuben and William Hirst. At the tower's base is a wide lift door opening with stone jambs and an I-beam lintel.

The stair tower at the south-west corner contains windows matching the main building pattern on its south elevation, with thinner windows to the left corresponding to the staircase stages inside. The west-facing windows are more ornate, forming pairs in arched Italianate stone frames with central square mullions and moulded bracketed sills. The stair tower has a thin cornice matching the main block and a cast-iron water tank with pitched roof. The roof of the Spinning Block is multi-pitched and hipped to each main elevation, with three parallel pitched roofs running east-west and two shorter pitched roofs running north-south. Roof lights penetrate the northern section of two of the east-west roofs.

Internally, the Spinning Block employs fireproof construction with two rows of cast-iron columns, cast-iron beams, and transverse segmental brick arches up to fourth-floor level. Cast-iron columns continue to fifth-floor level, though the roof structure at this level is timber and unfireproofed.

At ground-floor level, the columns are cylindrical with moulded capitals and plain bases, featuring square-section bolting heads for power transmission systems on all four faces. The walls are of pier and panel construction, with thick brick piers to north and south walls supporting beam ends and thinner panels containing windows. The floor is finished with a concrete screed.

At fifth-floor level, the columns are cylindrical with square-section bolting heads. The capitals have brackets and shoes fitted around timber beams. The multi-pitched roof is supported on three-span timber king-post trusses.

The stair tower contains a central brick shaft, rounded on its western side and with a wide square-headed opening to its eastern face. The opening has a stone surround (now painted). The shaft was probably originally designed to supply water from the iron roof tank to a fire sprinkler system, though it has since been fitted with a lift mechanism and retractable lift doors on each floor. On the fifth floor, part of the mechanism bears the name "Fred Ellison and Co Ltd Bradford". The floors within the staircase tower are of stone flags, and a stone staircase winds around the shaft. The inner stairwell face is brick (now painted), with storage areas in the north-west and south-west angles closed with timber doors.