12 Segontium Terrace, including forecourt railings

12 Segontium Terrace is part of a late Georgian terrace consisting of nine three-storey, two-bay houses, featuring slate roofs and brick or roughcast stacks on the right side. The entrances are located in the left-hand bay and are 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 to 19 have a larger footprint than those numbered 11 to 14 and project forward at the rear. They also preserve original architraves on the front elevation, while houses 11 to 14 display late 19th-century details. The late 19th-century rendered front features eared and lugged architraves, along with sill bands in smooth render. The doorway is set within an added gabled half-lit porch and includes a replaced half-lit panelled door. The windows are primarily four-pane sashes, except for the upper left window, which is blind.

This terrace is part of the group of buildings at 11-19 Segontium Terrace.