Buildings 20a and 21, former rolling mill at Elsecar Ironworks, including two halved colliery pit wheels

Former rolling mill at Elsecar Ironworks, built in 1850 and extended in 1860 for Dawes' Elsecar Ironworks. The building was renovated in 1990 as part of the Elsecar Heritage Centre to serve as an exhibition and function venue.

The structure comprises a tall single-storey building of 12 bays with a cast iron framework and coursed sandstone gable ends. The side walls are infilled with coursed sandstone on the eastern side and brickwork on the western side, topped with a Welsh slate roof. The northern gable is set at an angle, creating an additional stone-built bay on the west side.

The cast iron framework features round-section columns with simple capitals and bases, many now buried beneath the raised external ground surface. These columns function as rainwater downpipes and support cast iron beams forming shallow basket-arches with perforated spandrels divided by vertical struts. On the western side, one column is omitted, with the double bay spanned instead by a substantial riveted wrought iron girder.

The substantial stone-built gable ends are quoined and wrap around the corners for structural stability. They are raised and coped, and originally featured tall round-arched windows, now blocked. The northern gable has been at least partially rebuilt, removing external evidence of a former railway siding access; the buttresses flanking the blocked entrance are probably twentieth-century additions.

The infill panels to the side walls show evidence of different construction phases and numerous later alterations. Windows within these panels are generally iron-framed with small panes, while doors are typically timber-boarded.

On the eastern side, panels are mainly stone-built with some having top portions in brickwork. The southern three panels are blind. The next three each contain a pair of large windows with stone lintels, the southern two enlarged into doors. The following three panels have smaller paired windows with segmental heads formed from two courses of brick headers. The next panel is late twentieth-century with large double doors set in brickwork. The final two panels are largely obscured by a mid-twentieth-century addition.

On the western side, panels are mainly brick-built in pier-and-panel construction typical of late nineteenth and early twentieth-century industrial buildings. The additional stone-built bay at the northern end includes a single tall round-arched window. The next six bays are infilled in brickwork, each divided into two panels with segmentally headed windows; two of these bays have been altered with inserted doorways replacing windows. The remaining bays are of later, plainer brickwork with various openings.

The original roof structure features 13 Howe trusses formed with timber principal rafters fitted into cast iron sockets at the column tops and ridge, with remaining truss elements composed of rolled and wrought iron sections and rods. Most iron elements are in tension, typically arranged as paired strips bolted through to clasp compression elements of T-section. Between the original trusses are more recent Fink trusses, possibly added around 1990, formed from lighter-weight sections, probably steel. The interior includes various additions and structures installed during the 1990 conversion to a function venue and subsequently.

Set into the ground adjacent to the north gable are two halves of a spoked colliery pit wheel, likely sourced from one of Earl Fitzwilliam's collieries and potentially manufactured at Elsecar Ironworks.