Trefaes Isaf and front garden walls and railings

Trefaes Isaf is a farmhouse built from rubble stone, featuring a slate roof and large stone end stacks. The eaves are supported by paired brackets. It is a two-storey building with a three-window front that is offset to the right. The upper floor has 9-pane hornless sash windows, while the lower floor has 12-pane horned sash windows flanking a central door with a 3-pane overlight. The windows are adorned with stone voussoirs and stone sills, and the gable ends have bargeboards. The rear wing includes a large end stack and fretted bargeboards on the gable, with a door in a 20th-century porch to the left of the left gable of the main house. There is also a hornless sash window on each floor to the left, with a 9-pane window above and a 12-pane window below.

The front garden is enclosed by stone walls on each side and features iron railings and a gate between piers topped with ball finials.

Inside, the farmhouse has a well-preserved early 19th-century interior, which includes six-panel doors and a central stair hall with a closed string, ramped rail, and turned newels. The lower flight has square stick balusters, while the second flight and landing feature turned balusters. There is a panelled door leading to the understair area. The left room boasts a large fireplace with a painted timber rack above it. This rack has four plank uprights that are cut with curved slots and hearts, designed to hold rods or poles but not gun stocks. On the first floor, there are three six-panel doors. The kitchen in the rear wing has a panelled timber partition to the left of the door, and the fireplace has been altered. Stone stairs lead down to the cellar from the kitchen, and there is a four-panel door connecting the kitchen to the front range.