Former model lodging house for GWR workers, later Wesleyan chapel

Former model lodging house for Great Western Railway workers, begun in 1847 and revised and completed in 1853–5. The building was converted to a Wesleyan chapel in 1869, remaining in use until 1959. It subsequently served as the Great Western Railway Museum from 1962 to 2000, and is currently used for education and performance.

The building is constructed in ashlar limestone with asbestos cement roof slates. It has a roughly square plan, comprising a full-height open former chapel to the east and three-storey former lodgings to the west.

The exterior is in Gothic style with additional 13th-century-style pointed-arched windows. The original main elevation to Emlyn Square is three storeys in height, with four-storey end bays and a central entrance. A projecting, pitched and gabled porch was added in 1869 upon conversion to a chapel. This porch houses a pointed-arched doorway with hood mould and label stops, with the inscription "WESLEY / CHAPEL / 1869" above. The end towers have canted corners and buttresses with offsets, corbel tables and parapets with rectangular ashlar stacks to the hipped roofs. The ground floor displays trefoil-headed paired lights with transoms, which are shouldered to the first and second floors. Those on the second floor are raised as gabled half dormers. The end bays have similar triple light windows. The main elevation to Faringdon Road is comparable but features a large central gable with lancets and gable lights between a pair of later square stair towers, returning by broaches to octagonal louvred turrets above the second floor. The ground and first floors have been altered by the creation of double-height glazed openings associated with the building's late 20th-century use as a railway museum, now partially infilled in limestone. The south side has had its ground- and first-floor windows replaced with pointed-arched, traceried windows and a large doorway, whilst those to the second floor have been retained, with some applied tracery. The east wall, constructed in limestone rubble during the 1860s conversion to a chapel, has double-height windows with tracery.

The interior original main range behind the west elevation contains a stone staircase at either end, rising through the three storeys of the central bays. Ground-floor rooms are set off a rear corridor with red quarry-tiled floor and black tile margins. The former porter's room with fireplace is at the south-western corner. At the north-west corner, the site of a former copper boiler is set at the top of steps to the basement, which retains a narrow fireplace opening. The first and second floor rooms, originally also accessed from a rear corridor, now have modern suspended ceilings. At either end of the range are rooms in the attic of the four-storey end bays, accessed by hatches. These attic rooms remain unaltered since the building's use as a lodging house, retaining their four-panelled doors pierced for ventilation, fireplace openings and some 19th-century wallpaper. The roof structure is king-post. The remainder of the building is occupied by the double-height former chapel. The west wall has high, traceried internal windows overlooking the former chapel from the rooms in the main range. The former chapel has a panelled ceiling divided by heavily-moulded beams carried on double-height, keeled cast-iron columns with pierced brackets featuring quatrefoils.

Iron railings with fleur-de-lys heads, set in a limestone ashlar plinth, run between the buttresses and the jambs of the porch to the west elevation. Gates made of similar uprights enclose the porch.