20 South Street and building to rear

This building was listed Grade II* in 1983 with the following description:
'Former engine manufactory of Robert Stephenson & Company. Boiler/plate shop and administrative offices c.1849-59 as part of the Stephenson Company Factory. EXTERIOR: Boiler shed red brick; offices hard white brick with tooled ashlar dressings; Welsh slate roof with glazed skylight strips. Former offices are on South Street front at NE of site, with former boiler shed an irregular L-plan around them with full length double span N-S roofs at west. East elevation to South Street has former boiler shed to left, former offices at right: 1 and 2 storeys, 4 and 8 windows. At left, former boiler shed has wide loading door and vehicle entrance below reused large bellied iron beam, made up of riveted sections and with central hole as in a pivoting beam, inserted below heads of 4 round-arched brick windows all now blocked. The rear wall of the boiler shed, to the former Sussex Street, is an impressive feature, being largely glazed and having the original frames with glazing bars. On South Street the former offices at the right are in a domestic style with stone plinth, first floor and sill bands, and eaves cornice. All brick openings have outward splay. Chamfered projecting plain stone surround with cornice to double leaf 4 panel door and plain overlight in 7th bay; wider double door with 4 flush panels and plain overlight in 3rd bay; flush door and plain overlight inserted in former window opening in 5th bay. first floor band. Sashes with fine glazing bars have sill bands and wedge stone lintels. Stone eaves gutter cornice. INTERIOR of 8 bays is domestic in layout with 6 panel doors in the two main upstairs rooms to the east - formerly the Managing Director's room and the Boardroom and 4 panel doors in the Drawing Office with a large chimney piece in the MD's room and slightly smaller ones in the remaining offices. Some C20 features including a chimney piece and office fittings, and wall hatches. The stair opposite the main door in a rounded projection into the boiler shed, is of c. 1840 character with winding stone steps which had decorative cast-iron balusters with narrow mahogany handrail. It leads to a long corridor which opens into a further office, behind this domestic building, inserted as first floor timber-framed projection over boiler shed, supported on iron columns of the shed which have curved braces to the roof beam. It is glazed above the dado. At the north end of the rear office a large list is inserted. Behind this office range, the boiler shed has 2 parallel ranges, the eastern range of 13 bays, the western of 17, supported on the west by the large glazed brick wall, and internally on tapered round cast-iron columns with curved longitudinal bracing to beams. The eastern roof has strutted king posts, the western has queen posts with small king posts resting on the collar. HISTORY: The western range was probably erected first c. 1849 together with the western range of No. 18, South Street [now demolished]. Both were built on the site of the former boiler/plate shed. The building was rapidly extended eastwards incorporating new offices c. 1859, built to replace the first company offices erected in 1823. Slight internal adjustments made c. 1867, such as the raising of the floor level and steps in the two northern office rooms plus a very small area of the northern workshop wall. Under the 1867 lease there was necessary agreement for rebuilding due to the demolition of Foster's Court and the extension of the offices northwards. The lease also states that Robert Stephenson & Co. were already in occupation of the premises now called No. 20, South Street. The large boiler/plate shop and offices retain many of their original features. These structures are of interest as examples of relatively un-altered industrial buildings of the 1840s-60s and gain additional importance from having been part of the R Stephenson Co. locomotive factory which occupied the site between 1823 and 1902.' LISTED GRADE 2*