Tan yr Allt Isaf

Tan yr Allt Isaf is a farmhouse, dating to the 18th century, built of limewashed rubble stone with slate roofs and end stacks. The building has a two-storey, L-shaped layout, comprising a two-unit main range and a single-unit wing. The present entrance is located in the angle formed by the main range and the wing, with a secondary entrance on the wing's outer side. The windows are 12-pane sashes on both floors; while those in the main range appear original, the masonry around them has been disturbed, suggesting later alterations. The right-hand unit of the main range sits upon a rough, heavy plinth, hinting at a potentially earlier, separate construction phase.

Inside the main range are roughly chamfered axial beams. The wing contains an axial beam with run-out stop chamfers, and a deep fireplace built into its gable end.