Number 20 And Building To Rear (Number 18 Now Demolished)

Number 20 and Building to Rear (Number 18 Now Demolished)

Former engine manufactory of Robert Stephenson & Company. This Grade II* listed building comprises a boiler and plate shop together with administrative offices, constructed between circa 1849 and 1859 as part of the Stephenson Company Factory.

The exterior presents contrasting materials: the boiler shed is built in red brick, while the offices are constructed in hard white brick with tooled ashlar dressings. The roof is Welsh slate with glazed skylight strips. The former offices occupy the north-east of the site, fronting onto South Street, while the former boiler shed forms an irregular L-plan around them, with full-length double-span north-south roofs to the west.

The South Street elevation shows the boiler shed to the left and the former offices to the right, comprising one and two storeys with four and eight windows respectively. The boiler shed features a wide loading door and vehicle entrance beneath a reused large bellied iron beam made up of riveted sections and incorporating a central hole characteristic of a pivoting beam. Below this beam are four round-arched brick windows, now blocked. The rear wall of the boiler shed, facing the former Sussex Street, is largely glazed with original frames and glazing bars, forming an impressive feature. The South Street offices adopt a domestic style with stone plinth, first-floor and sill bands, and eaves cornice. All brick openings have outward splay. The main entrance comprises a chamfered projecting plain stone surround with cornice framing a double-leaf four-panel door with plain overlight in the seventh bay. A wider double door with four flush panels and plain overlight appears in the third bay, with a flush door and plain overlight inserted into a former window opening in the fifth bay below the first-floor band. Sashes with fine glazing bars feature sill bands and wedge-stone lintels beneath a stone eaves gutter cornice.

The interior of the eight bays follows a domestic layout. The two main upstairs rooms to the east—formerly the Managing Director's room and the Boardroom—contain six-panel doors, as does the Drawing Office with its four-panel doors. A large chimneypiece occupies the Managing Director's room, with slightly smaller examples in the remaining offices. Twentieth-century features include a chimneypiece and office fittings, along with wall hatches. A staircase opposite the main entrance, contained within a rounded projection into the boiler shed, dates to circa 1840 and features winding stone steps with decorative cast-iron balusters and a narrow mahogany handrail. This leads to a long corridor opening into a further office, which comprises a first-floor timber-framed projection over the boiler shed, supported on iron columns with curved braces to the roof beam and glazed above the dado. A large light insert appears at the north end.

Behind this office range, the boiler shed comprises two parallel ranges: an eastern range of thirteen bays and a western range of seventeen bays. The western range is supported externally by the large glazed brick wall and internally by tapered round cast-iron columns with curved longitudinal bracing to beams. The eastern roof features strutted king posts, while the western roof employs queen posts with small king posts resting on the collar.

The building's history reflects successive phases of development. The western range was probably erected first around 1849, together with the western range of Number 18, South Street (now demolished), both constructed on the site of the former boiler and plate shed. The building was rapidly extended eastwards with new offices circa 1859, replacing the first company offices erected in 1823. Slight internal adjustments were made circa 1867, including the raising of floor levels and installation of steps in the two northern office rooms, plus a very small area of the northern workshop wall. The 1867 lease document required rebuilding due to the demolition of Foster's Court and the extension of offices northwards, and confirms that Robert Stephenson & Company were already occupying the premises at Number 20, South Street.

The large boiler and plate shop and offices retain many original features, exemplifying relatively unaltered industrial buildings of the 1840s to 1860s. Their significance is enhanced by their role as part of the Robert Stephenson & Company locomotive factory, which occupied the site between 1823 and 1902.