The former Tread-wheel House at HMP Shepton Mallet

The former Tread-wheel House at HMP Shepton Mallet is a late-18th century building, constructed of exposed rubble limestone with stone ashlar dressings and a slate roof. Originally a unique feature of the prison, it was built on a rectangular plan and formerly contained tread-wheel and gear wheels arranged vertically, with access provided via a series of walled yards to the front, and hospital rooms located above.

The front elevation features a row of ten segmental arches at ground-floor level, which originally opened onto a series of walled yards that ran the full length of the building. These yards could be overlooked by guards from a stone inspection terrace. Prisoners accessed the six sections of the tread-wheel from the yards, and the positions of these are marked by six large segmental arches at first-floor level, now closed off. Access to the first floor is via steps located centrally and at the corners of the building, leading to a gallery that runs along the entire width. A stone rubble wall, enclosing the left-hand stairs, may have been part of the walls to the former yards. Narrow openings flank the six large arches, giving access to stairs leading to the former infirmary on the third floor. This upper floor has eleven multi-paned windows, with three taller window openings inserted at a later date.

The rear and north elevations of the building are blind, the north side forming part of the prison’s perimeter wall. The south end has a wedge-shaped lean-to, rising just under the eaves, with a central, segmental-arched doorway at ground-floor level and two narrow vents under the eaves. The rear of the lean-to forms part of the perimeter wall.

The interior was converted to offices in the early 19th century, with a floor inserted at the current first-floor level. Arches marking the position of the former tread-wheels remain visible. Ground-floor arches are now used for storage. No further fixtures and fittings of note survive on the ground and first floors. The top floor, formerly the infirmary, was not inspected, although the stairs leading to it remain.