Coed-y-Foel Isaf including adjoining Agricultural Range

Coed-y-Foel Isaf is a linear range comprising a 3-unit, one-and-a-half storey farmhouse with a rear wing and an adjoining agricultural range set down on the left. The building is constructed of local rubble with boulder foundations and has a medium-steep slate roof. It possesses an axial chimney and an end chimney to the rear wing, both with weathercoursing and plain cornicing.

The farmhouse has an off-centre entrance with a 4-panel door, positioned against the chimney stack, and a broad 8-pane sash window to its right. A 6-pane sash window is located to the left, and a further entrance with an early 20th century part-glazed door is situated at the far right. The upper floor features three six-pane sash windows within gabled dormers. The rear wing has six-pane, part-tilting modern windows to both floors on its return side. A single-storey catslide outshut projects outward to the left, flush with the gable end of the main block, filling the angle between the two ranges; a boarded entrance is on the right.

The agricultural range adjoins the farmhouse on the left, with a slatestone mounting block at the junction. It has a medium-steep roof and three doorways on the front. The two doorways on the right have crude projecting slatestone lintels, with similar window openings flanking the central entrance, which has boarded double doors. The left-hand entrance has a boarded door and a window to the left, which is a reduced former entrance. The rear of the agricultural range has an entrance on the left with a 19th century catslide dormer to the roof and a part-boarded window. Central boarded double doors lead into the range. A catslide projection extends to the right with steps leading up to a boarded entrance on its return side. Two further boarded doors are present on the main face, with a plain window opening in the centre.

The farmhouse has a lobby-entry plan with a central hall and a former parlour to the left, and service rooms to the right. The hall features a large fireplace with a roughly-chamfered bressummer. It has a chamfered main ceiling beam with plain joists, and a similar beamed ceiling to the rear chamber. The agricultural section is divided into 6 bays, with rubble partitions between bays 3 and 4, and 5 and 6. It exhibits pegged collar trusses and tie-beams with raised crucks to the end bay on the right. This bay also has a rough beamed ceiling with a 19th century stick baluster stair leading to an unheated, plastered farm labourers' dormitory on the loft floor, which also has a stick-baluster landing.