Former Byre at Castle-upon-Alun House

The former byre at Castle-upon-Alun House is a single-storey building with an attic, oriented north to south. It is constructed of rubble stone and topped with a slate roof. The front of the building faces east and features a wide segmentally-arched opening on the left, which has stone dressings. The stonework appears to have been reused from another structure and includes roll mouldings. The sides are made of large stone blocks, with eroded broach stops on the right side. To the right of the archway, there are three stables, each with boarded double doors. The outer two doorways are supported by large concrete lintels, while the central doorway is adorned with a gabled pediment that has mouldings. There are also two hay loft hatches to the right and center, each with planked doors.

An exterior staircase with stone boundary walls leads to the south gable end, providing access to a boarded door into the attic. On the left side, there is a horned sash window set in a brick surround beneath a relieving arch. The rear of the building features a six-pane window in the center, which has a flat concrete lintel, with possible blocking to its left. The north gable end includes a small two-light window.

Inside, the stables are fitted with concrete partitions and floors.