Former Gas Retort House, Retort House Extension To South West And Attached Store

Former Gas Retort House, Retort House Extension and Attached Store, Gas Street, Birmingham

This is a former gas retort house with attached extension and store, now converted to workshops and standing empty at the time of inspection. Built in 1822 for the Birmingham Gas Light and Coke Company, it formed part of one of the earliest provincial gas works. A retort house extension with attached store was added in 1828. The building was altered in the late 19th century and again in the 20th century.

The structure is constructed of red brick beneath a corrugated iron roof covering carried on a cast iron roof structure. The roof is formed of cast iron roof trusses, linked by transverse and longitudinal wrought iron tie rods. The building follows an L-shaped plan, now considerably modified internally, with a narrow frontage to Gas Street.

The north-east elevation features a rendered and painted facade with a blind recess to the north-west beneath an elliptical arch and a tall double doorway to the south-east with a flat head. A shallow parapet above a moulded cornice band conceals the roof hip. The side walls are substantially artexed. The south-west side wall was originally substantially an open arcade supported by slender cast iron columns, three of which survive and are incorporated in later back infilling which contains blocked semi-circular headed arches. The north-west side wall contains three blocked doorways and a semi-circular headed window at the north-west end of the cross range, together with 20th-century openings.

The interior consists of a main range of eleven structural bays with a five-bay cross range extending north-westwards. The roof is carried on two-piece cast-iron trusses bolted together to form a 35-foot span, the outer ends supported on flat cast-iron plates set within the brick walling or mounted on the tops of cast-iron columns. The trusses feature diagonal lattice work webbing which links the inclined upper members to a segmentally arched soffit. The trusses are linked longitudinally by a cruciform section central purlin bolted to the central lap joints of the trusses. Modified truss castings are used for the hipped ends, and at the junction of the two ranges a large diagonal truss spans the diagonal angle. Horizontal wrought-iron tensioned tie rods link the truss feet. The inclined upper face of the trusses is notched or toothed to accept metal roof lathes which were wedged in position and to which the original roofing slates were attached.

The extension to the retort house at the south-west end comprises five bays with four cast-iron trusses of slightly modified design mounted on cast-iron wall plates. To the north side of the extension was added a five-bay single-storey building, thought to have been a coal store. The roof is carried on four strutted queen-post trusses supported on brick side-wall piers. The queen posts extend above the line of the original roof covering and appear to have carried a louvre.

The Gas Street gas works was established in 1818, the retort house being the only survivor of the complex. The works were designed by Samuel Cleg (1781-1861), the first specialist gas engineer. The innovative metal roof structure represents a rare example of early advances in metal roof design made in the early 19th century. This example combines wrought and cast-iron constructional techniques, designed to prevent the internal thrust of the trusses being transmitted to the side walls—an important consideration for a roof which had to withstand the high temperatures generated in the gas-making process. The components for the roof structure are thought to have been produced in the Phoenix Foundry, Snowhill, Birmingham.