Old house, including attached bakehouse, at Llettyrychen Fawr Farm

The Old House at Llettyrychen Fawr Farm is a 2-storey building constructed of rubble stone with a roughcast front. The right-hand unit has a slate roof, while the left-hand unit's roof has collapsed, featuring coped gables. A central stack has been removed, and the left gable end includes a corbelled first-floor stack that has been reduced to below ridge level. Most windows have lost their glazing.

The front of the house features a 16th-century doorway to the left of center, framed by a chamfered dressed-stone surround with a four-centred head. To the right of this doorway is a window, followed by a former doorway that is now partially blocked, leading to the original hall, with a single window to the left. The upper storey has three windows. The right gable end shows the scar of a former attached dairy, while the left gable end contains a single 4-pane horned sash window and dressed stone jambs of an earlier window. The rear elevation has collapsed on the right-hand side, while the left-hand side features a lean-to hall bay with a small single-light window in its side wall, along with windows on each storey that have wooden lintels and a wide inserted doorway.

Attached to the rear left, or northwest angle, is a 2-storey former bakehouse made of rubble stone with larger quoins, behind which is a roughcast lean-to that connects to the main house.

The house follows a 2-unit lobby-entry plan. The hall, located on the right side, has a timber lintel above its large fireplace. The upper-storey floors have collapsed, and the room above the hall features three 16th-century arched-brace trusses. The bakehouse contains a large fireplace.