Siloh Chapel, including Schoolroom to rear, and attached house (18 Gloddaeth Street)

The Siloh Chapel, together with a rear schoolroom and an attached house at 18 Gloddaeth Street, was built in a Baroque style. The chapel is constructed of red sandstone and grey limestone, with a slate roof. The upper floor is faced with limestone blocks and sandstone ashlar dressings; the ground floor is rusticated, and the building is topped with a balustraded parapet and cupolas faced with sandstone ashlar. Projecting end bays on the north-east elevation feature quoins on the first floor and are crowned by domed cupolas. First-floor windows incorporate shouldered architraves with keystones and broken triangular pediments, with segmental pediments above eaves level; ground-floor windows are flat-arched with keystones. A central bay also projects, containing a Venetian window on the first floor with rusticated Doric columns and Ionic pilasters, surmounted by a broken triangular pediment. A wide portico on the ground floor features an entablature and segmental pediment bearing the word “Siloh” in the tympanum and inscriptions in the frieze, reading “19 Addoldy y Methodistaid Calfinaidd 05”. Intermediate bays are characterised by balustraded parapets and narrow windows on both floors, with the first-floor windows having rusticated pilasters and entablatures, and balustrading to the apron. The south-east elevation comprises six bays, with projecting bays at each end, the north-easternmost continuing the articulation of the corner bays of the north-east elevation. The south-easternmost bay features a Venetian window on the first floor and a plain window on the ground floor. Four intermediate bays have semi-circular headed windows on the first floor with moulded heads and keystones extending to the eaves cornice, with plainer openings on the ground floor. The north-west side elevation mirrors the south-east. Behind the chapel is a single-storey schoolroom block with a hipped slate roof. Attached to the rear, facing Gloddaeth Street, is a two-storey, three-window house constructed of grey rock-faced stone with a slate roof. Its first floor has three paired Gothic windows with sash glazing. The ground floor features, from left to right, a square bay window with two sash windows, a doorway with a boarded door, a splayed bay window with sash glazing, a further doorway, and a square bay window matching the other end.

Inside the chapel, a gallery runs along three sides, supported by slender fluted iron columns. The ceiling is divided into rectangular panels with circular panels inset within them. A wide arch is situated over the organ behind the sedd fawr.