West and south ranges of building at former quarrymen's barracks to north-west of Ty Mawr

The complex consists of two long rectangular single-storey ranges aligned north-south, located to the north-west of Ty Mawr. The eastern range served as barracks, while the western range functioned as a cowhouse. These ranges are linked by a dry slate boundary wall, with another boundary wall and a later, lower range to the south forming a courtyard.

The cowhouse is constructed from roughly coursed rubblestone and boulders, with some repairs and alterations made using squared slate slabs, and it has a slate roof. The original cowhouse features four door openings: one with boarded double doors, one stable door, and two on the right with missing doors. There are three small windows, one of which has a 19th-century horizontal sliding sash. The structure includes slate lintels throughout and an integral end stack at the right-hand end, which, like the corresponding section of the barracks range to the east, appears to be an extension. In front, there is a cobbled path with a boulder-lined drain.

The south gable end of the cowhouse has a stable door to the right and a small window to the left, with a blocked opening directly above at the apex. Attached to the east of the south gable end is the southern boundary wall, which features a wide gateway with slate menhirs as gate-posts. The roof of the southern range sits directly on top of the continuation of the wall to the east.

Inside, the cowhouse has nailed A-frame trusses with single purlins and a cobbled floor.