18 Segontium Terrace, including forecourt railings

18 Segontium Terrace is a late Georgian terrace consisting of nine three-storey, two-bay houses. The buildings feature slate roofs and brick or roughcast stacks on the right side. Each house has an entrance located in the left-hand bay, which is accessed by steps. In front of the houses, there are original iron railings on dwarf walls, adorned with pointed finials and cone finials on the stanchions, although the gates have been replaced.

Houses numbered 15-19 have a larger footprint compared to 11-14 and project forward at the rear. They also retain original architraves on the front, while houses 11-14 exhibit late 19th-century detailing. The façade is finished with scribed stucco and features a moulded eaves cornice. The doorway is set within a shallow, added 19th-century round-headed wooden porch that has panelled pilasters with blind lattice work. Inside, there is a panelled door topped by a radial-glazed overlight. The windows are four-pane horned sashes, housed in original moulded architraves that include keystones in the lower and middle storeys. The terrace belongs to a group with houses numbered 11-19 Segontium Terrace.