Barn and attached byre at Nant y Felin Uchaf

The building is a large barn made of stone rubble, featuring some dressed stone details and a mostly Welsh slate roof. Attached at right angles is a cowbyre range that has two levels, constructed partly of snecked stone and topped with a corrugated roof. The barn consists of six bays with opposing double doors; the front doors are set within a large gabled porch that includes an oculus above. There are four rows of ventilation slits on the gable end. Lean-tos are attached to the front on either side of the porch.

The cowbyre range, located to the right, has two units that are accessed from the farmyard at the front and from the rear at different levels. It features ventilation slits on the gable end, and smaller ventilators are present on the upper unit at the rear, along with sash windows and a door for the lower unit. This range is positioned at the lower end of the farmyard, creating a small yard, while the farmhouse is situated higher up. Opposite the barn is another range that includes brick dressings and extends to cart bays at a lower level.

Inside the barn, there are pegged trusses with tie beams and collars. The cowbyre has an A-frame roof and retains mangers in the lower unit.